I didn't play Evochron Mercenary MP so I can't comment.
Hmm. Well, to sum it up, EM did EXACTLY what you are describing, with VERY similar trade-offs (clearly the developer felt the same way.
). Instead of ships you had 'frames' and on these frames you would build your ideal ship. Each 'frame' had a variable, i.e. more armor, less speed, etc. Then you throw your favorite modifications and have a ship.
My personal problem with this, is that what happened, was that everyone flew the exact same 'frame' because it was best at a given thing. Combat, exploration, whatever. There was no reason to use a lower end frame, because the big one's trade off was worth the advance you got for doing whatever activity.
Now, with Frontier Elite 2 and Frontier First Encounters, one of my favorite things was how people used the tools they where given. I myself exclusively flew the Cobra Mk. III. I know of a Sidewinder pilot on this very forum, who swears by that ship. I also know of a Viper pilot who does the same. Despite the fact that you can only customize these so far, its how they use them that really makes them into something special.
Now, lets look at EM again, lets say I have a top combat frame. Everyone else who dogfights, is going to have that same frame, unless they don't have the cash. Even with customization, everyone essentially is flying the same thing, and forced to use the same tactics.
Now, I suppose EM may not have been balanced properly, and what you are saying could work, my fear however, is that without ships with very defined roles and attributes, we end up with everyone flying the exact same thing and loadout, with different colors. Granted you could probably do that with the older style ships, but they where fairly well balanced. A well stocked Cobbie, could easily handle a well stocked Asp given each ship knew how to use its advantages.