Great points, but to counter with the RP currently in play, well gaze at our current tech, the space shuttle which is 0.0825 tons unloaded, but at launch jumps to a whopping 2200 tons. I don't imagine mankinds first historical move is going to be building a 8k ton space monster because the necessary support tech would be ridiculously massive as to be impossible. By human engineering standards that would be the 10th wonder of the world in a space based medium. No humanities first move would be towards building smaller scale but significantly larger frames then the space shuttle, for the sole reason that the space game is not like earth based naval actions, at sea if your ship goes you have a chance of living because your still within your atmosphere, in space no such luck. I imagine mankind progressively building up, in the nuclear era (safety concerns aside), mastering the tuning/boosting process along the way, long before building into the uncertainty of Ion Drives.
I'm not sure if this game works like this or not but each era of drive tech should require their own seperate drive enhancement research tiers. Ie knowing how to boost a thermal drive 250% is not the same as knowing how to boost an Ion Drive, let alone these magneto drives I keep seeing. The 250% drive enhancement research shouldn't carry over if the drive is using differing energy principles, chemical, nuclear, Ion, magnetic. Human trends tend to rest in using a fuel source for extended periods of time, despite the awareness of alternative fuel sources, due to the cost of changing the dominant medium that all era tech is reliant upon, for various reasons.
For instance, magnetic field principles applied to a rocket frame would differ. A finely tuned magnetic drive emits a field around the object, freeing the object from external gravitational pull, friction. I imagine that gain impulse it inverts the magnetic field on itself. Ie the push field is warped towards the exterior space surrounding itself at a certain angle. then a matching magnetic push field is emitted from the hull. Using directional controls the field can be manipulated to push at certain angle. I image it had horrible research catastrophes when the field's directional control failed and a push vs push happened across the entire ships hull, literally crushing itself.
The point being, a magnetic missile would be efficiently designed as a saucer. the drive in the center to provide equal field distribution for movement, the area surrounding packed with explosives. Its payload would be monstrous compared to a traditionally missile design.
Though on reflection I could see how chemical/nuclear/ion would still use the same tech frames as their all just improvements in directed chemical/particle ejection. You point the engine this way, an the warhead this way.