pasuuli said:
Good points, but maybe not so difficult to overcome.
Ship design is modular, regardless of rules system. Add rules for inertialess drives; ST enabled, Traveller enriched. Similarly with weapons. After all, Traveller: The New Era rules made weapon ranges puny.
There is no problem with design sequences and technologies. After all, TNE and GURPS both allow for different technologies in their main technology books (Fire, Fusion & Steel and Vehicles, respectively).
Maybe technology is the most significant difference, but a compatible ST-Universe add-on for Traveller (or any rule system) could fix that. I think flavour is related to the movement and range considerations.
Definitely - and that is the problem. Once you change the movement and range considerations, you get different games.
For example: ACTA relies on non-vector movement. Thus it is relatively simple to close with your opponent and engage them. Even if you manage to overshoot your opponent, it is relatively easy to come about and engage him again. Fire arcs are quite important and dominate your tactics.
The Traveller-variant of Full Thrust (on the other hand) uses a vector and inertia-based movement system. It is perfectly possible to move in one direction and fire in another. Weapon arcs do not dominate your tactics. However, if you miscalculate, then you end up struggling to match your vector to your opponent's.
Then, there are problems matching different velocities as a result of different drive systems. This problem was highlighted best in the game Star Cruisers for 2300AD. The stutterwarp drive was capable of moving vessels at high velocities with incredible manoeuvrability. When they went up against normal rocket drives, they were at such an advantage that the rules treated them as stationary.
Even mixing similar backgrounds can have its problems. In SFB, the standard turn is 1 second, which is divided into 32 impulses. In the STIII:TCS, turns were of the order of 10 seconds (iirc). In theory a SFB Enterpirse could run rings around a STIII Enterprise - until it got to Warp 3.2 when it could not engage it in combat at all. however, past Warp 3.2, the STIII Enterprise could just merge warp bubbles and blow the SFB Enterprise to smithereens.
It is not impossible to write a starship combat game that covers all bases - especially if you use modular rules to cover different genres. However, by the time you have done that, I believe you may as well have written an entirely different game.