The issue (for me at least) is that using Jump as the focus for effectiveness of a TL fighting ability puts the higher Jump capable ship at a severe disadvantage. There is a straight computation of 10 percent of mass times the distance travelled for fuel. So a 10 000 ton ship that is Jump 2 has 2000 tons of space reserved for jump fuel. A J4 ship has 4000 tons of space reserved for jump fuel. Unless the tech advances can make 2000 tons of fuel not be needed a J4 ship will be at a disadvantage when fighting the J2 ship. The J2 ship has 2000 tons of space to add weapons and armour that the J4 ship does not.
Jump is a strategic capability, not a tactical one. In combat the Jump numbers mean nothing. They matter in getting to a system to defend it, the J4 ships will get there twice as fast, and allow more ships to be moved within the same time frame as a J2 fleet. This is the logistical and strategic side.
When it gets time to start shooting the Jump drives and fuel tanks are just taking up space.
Put a 10 000 ton Jump 4 ship up against the same tonnage of SDB monitor. All the extra space is put to armour, defense, weapons, ammo etc.
Taking things down to a small ship scale:
I am playing around with trying to remake the Drinaxian Harrier from the Pirates of Drinax. I am looking at a triple turret and Particle beams and pulse lasers advanced tech upgraded to Longer range. To me the higher tech advantage will end up in a higher TL fleet able to shoot and hit from a range band the enemy cannot shoot back from.
If you can have your computers run advanced software with enough spare bandwidth and extra sensor lock boons or banes against the enemy. Assuming the Gunner stats and skill levels are all the same it is the + DM's from the higher tech systems that will overcome the negative DMs from the range. If the enemy only has medium or long range weapons, and cannot match your counter thrusting to maintain distance they will not be able to shoot back since weapons do not reach past their band. Missiles may be able to cross the distance, but the point defense of a triple turret, and the thrust of higher tech ships may allow missiles to be outrun long enough to be picked off by the laser defense of the higher tech ship.
Meanwhile the radiation attack of the particle beam are killing crew. My redesign has very high damage output, all 1's an 2's are counted as 3's, so the minimum damage per hit is 15 points. This is enough to cause a critical from damage loss against a thousand ton ship, and multiple criticals against a ship of equal size.
The higher tech base has my J2 Harrier stealthed and attacking from hiding for the first attack, so a double hit from very long range may be possible in the first round. I am not finished with the design, but even idly rolling a few rounds of combat against the various ships in the common spacecraft section is making me thing that it is the range capability, and the bandwidth of the computers that offer the best Tech advantage. Even in a straight head on fight my tactics are to stay at very long range and chew the enemy to pieces. Nothing better than to take on an 800 ton mercenary cruiser and roll 7 three times in a row on the Critical Check to chew through the Hull.
Your conclusions may be different, but the linear use of fuel (minus the small percentage allowed for in tech reduction advantage will not allow the J4 ship to pack as much punch as a J2 ship since it gives up 2000 tons of space in the same size hull for fuel.
Now change that to Collectors at Tech 14, and get rid of fuel altogether, or go Psionic and things change even more, but we get further away from that Old school Traveller feeling.
(not that I would mind delving into the areas of Psionics and Collectors, I have already posted on here about both topics)