The different approach is because of the different design systems. In MOO you could get a 'reward' for making a ship less than the max weight. It could be a bit faster and more maneuverable. In SE there is no difference in the ship's maneuvarability if it has less than the absolute maximum amount of equipment that can be stuffed into it. So, while you could re-arrange the tech fields in SE to work more-or-less like they do in MOO -- giving smaller Versions of the same tech instead of more powerful Versions at the same size -- you would not get the same rewards even then. It would be interesting to see AIs cram more & more weapons into their ships, though. With missiles this could either become unbalancing, or it might correct the balance problem vs. PDC.
You know, I think the MOO style is better because it doesn't encourage you to 'hold back' on using your latest tech until you get some more levels. You get full performance of your new tech right away, it just uses more space.