Inertia doesn't make dogfights unrealistic. It just changes the techniques and makes them look pretty crazy and wild to our eyes. Some episodes of Battle Star Galactica give this vibe, though they weren't very consistent about it. The Expanse episode where the Rocinante attacks the space station is a good example of a dogfighting in space sequence. It is not a matter of taking this fun thing away by insisting on boring science: rather it is a matter of knowledge of how this fun thing would actually work in space, (or not knowing and doing it wrongly (which actually makes it a less of a fun thing in the end) ) . The main thing to get a dogfight started is that you need to be on close to identical vectors and in close proximity. This you can do if you have a lot more thrust than your opponent and don't get shot down on the apporach.
One typically does not "dogfight" a stationary object. BG cheated the hell out of the inertia by doing basically SW maneuvers - Cylons and Vipers would be accelerating towards one another and then instantly flip and accelerate in the other direction.
It's quite true that dogfights with inertia would be much different than we would expect. The only way TO have a dogfight would be to have similar courses and speeds and then to have the two side interpenetrate. To stay in range one, or both, sides would have to not attempt to radically change velocity or heading.
A better comparison would be sailing ships with cannons at close range, just slugging it out. There would be no real "dog fighting", nor strafing runs of inbound fighters on enemy starships - they would have a moment of time where they were within weapons range and then the two sides would be past one another.
There is no reason ships couldn't spin to point their weapons at their targets, shoot and then spin back regardless of heading. In fact, that's what they usually do in Traveller, to judge from the RAW. RAW ships shoot all their weapons every turn at any target they choose in range regardless of firing arc, which implies they are spinning around as needed. It is what happens in the Expanse when ships shoot each other, and it looks really cool and exciting.
Only the fact that you have, in some cases, extremely large ships trying to rotate on their axis like they were dainty and nimble craft. That's where the Traveller mechanic fails. And this also ignores the fact that you cannot continue to thrust along your course while doing so. In order to maintain your baseline course you'd have to stop your thrust along your current axis, spin, fire, spin, then resume thrust. All the while the ship pursuing you would be continuing to maintain it's thrust, thus if the two ships have similar thrust ratings the ship in pursuit would catch up due to the simple fact it's never had to stop thrusting.
I'm aware the rules don't take into account that weapons, aside from spinal or fixed mounts, can be brought to bear on any target within a 360 degree sphere. I was pointing out the fact that there is a built-in fallacy to this using the rules as written (i.e. inertia). One can simply hand-wave aside the fact that maneuvering thrusters are extremely powerful, or else ships have very little mass, thus they are able to perform like ballerina's in space. These concepts seem at odds.
Nobody has a "standing start" ever. The concept is meaningless. Each ship has a vector or an orbit around some object, unless it is sitting on the object. What that vector is, is a part of figuring out if you can intercept another ship - just like it's distance from your ship is. This doesn't change the overall possibilities of interception - it just means that you have to know two things about each ship: their location and vector.
True, everything in the universe is in motion at all times. However you are ignoring the fact that there is relative motion and universal motion. Objects in our solar system rotate around our sun, which itself is rotating in our galaxy. Ergo all things have motion, but it's also relative to the location you are at. Thus if you are at a "standstill" relative to the system you are in, you will remain in that location until some other objects gravity affects you. Thus you are at a "standstill". I figured that is implied when talking about such things, but obviously that was not how it was taken.
You seem to ignore the fact that in addition to location and vector, one also must account for acceleration. A ship exiting jump space, per RAW, maintains the heading and velocity that it entered jump space. Thus a ship lying doggo (for you that means a ship that is not under acceleration in the local system and essentially is drifting) must begin accelerating to catch the ship that exited jump space. Assuming said ship had been accelerating for hours to reach the 100D jump radius, the ship trying to intercept has very little chance of success before the arriving ship is able to make planetfall, or at least get within range of planetary assistance.
There is no such thing as a "known jump route". This idea also makes no sense. Planets are the usual destination for ships and they are always in motion. So what would a "jump route" be? Any point in space or route where a jumping ship might appear to fly to a given planet will be in a very different location relative to that planet tomorrow, and a year from now it will be outside the star system in question entirely.
Sigh... Yes, all things are in motion. Again you miss the point of the statement. I'm assuming you understand space is pretty big? And the volume of space at the 100D limit or beyond is also rather large? Which means it should be nigh impossible for ships to ever be caught by a pirate since inbound ships can choose their arrival locus? A clever pirate though can also run a navigational plot to know that ships inbound from a particular system tend to arrive in a general area, and they can also backplot a rough route that ships departing the other system tend to take. Whether or not ships would prefer to arrive above or below the elliptical plane is a guess for anyone to make - its not discussed. I tend to think that it's possible to narrow down such a volume of space.
Those known points will always be somewhat known since ships in jump follow a linear path from origin to destination - and any ship can plot the masses large enough to bring them out of jump space, ergo you can narrow things down to the most common/likely emergence area. Inbound ships still have to deal with the 100D limitation of their arrival planet, which gets back to the idea of where exactly they may choose to emerge. Per your previous point, an inbound ship would most likely want to emerge at a location where it can take advantage of the planets movement and minimize having to "catch up" to it while flying along the same orbital path. Or at least emerge at a location where it is relatively neutral for orbital velocity. This doesn't address the fact that the emerging ship already has a heading and built-up thrust vector, but that's an entirely different discussion.
There is hope for aspiring pirates however, Finding ships in interplanetary space is difficult, but they come to gas giants and other fuel sources, where you can intercept them. Also, if you know where they are going and how fast they are thrusting you can find them by doing the math. Pirates need spies, sensor buoys and small craft scouts. Intelligent pirates don't pop up in well patrolled parts of well patrolled systems.
But do they really take days out of their schedule to go get free gas giant fuel when they can buy all the water they want at a starport and refine it themselves? Simple math tells you that the time spent travelling to a gas giant, refuelling, and then moving out to the 100D limit of the gas giant is woefully uneconomical from an operational perspective.
Once you take the other parts of the rules into account, piracy becomes less and less likely from a pure surprise perspective. There are just too many strikes against it. Not to mention that paying for the spies, sensor buoys and scouts makes it more like a business than a "arr, avast ye mateys!" type of operation.
Erasing inertia somehow via technology raises all kinds of issues and questions which would have to be worked through, and these are really problematic for maintaining an interesting setting. All the physically impossible magic future techs in the game raise issues of how they interact with the game universe - witness all the discussions about jump drive's preservation of momentum or not, and m drives smashing asteroids into planets. These techs , or ones like them, are needed for the game to make the space opera work, though, so we have to do the work of figuring out how they interact with the rest of physics. Magic inertia erasers, however, don't add to the game, and so we don't need to do this work.
Aside from players thinking that smashing objects travelling at fractional C velocities is a good way to wage war, I don't see much in the game that speaks to that thing. The idea of inertia and preservation of momentum going into/out of jump space is just fine - but that also means you have to throw it out the window when the rule book states that when having an encounter the two ships are now at essentially zero velocity. Thus your fat and bumbling merchants will always get caught by pirates.
I think it's far better to resolve these things within the core structure of the game. Doesn't really matter if you have magic intertia erasers or not - so long as the gaming universe remains consistent and you don't argue up a storm in defense of the system while poo-pahing criticisms of where it breaks its own rules. As you say, it's space opera, thus it's already outside of the realm of today's existence. Thus if you have jump drives and anti-gravity and all other kinds of theoretical science, there's nothing inherently wrong with making the rest of the system live within the boundaries you have already defined.
