There have been a few comments to the effect that engineless designs are unbalanced and the suggested solution is to require engines on most maps or force people to use them by combining them with reactors.
I propose another solution which retains the freedom in design, but would make it more advantageous to use engines: make engines generate power, but don’t take the reactors out. This way if you need power you can use reactors (which give you loads of energy) or engines (which give you some energy and enable you to move. Fast ships suddenly become a lot more viable because they generate all their energy without require reactors while engineless designs get an advantage i more efficient power generation, but don’t get a huge number of extra modules. A lot of designs at the moment might call for a level III and a level I reactor to power the ship as well as an engine to move. Under this scheme, you could replace the level I reactor with an engine.
Overall this should lead to faster ships and more freedom of choice and better balance rather than restricting anyone’s choice.