as someone who did toyed a little with huge models (real sized planets) as well as near warp speed travel and stuff like that, I can say is possible to work with giant models with some scaling trickery, the UI allows you to change "scales" of speeds and distances, working with this, means you can actually shrink everything and make everything slower, allowing you to create models that look "huge", however in some overly complex models, some discrepancies start to happen in the collision detection department, probably related with decimal points, refresh rate of the engine and/or simple accuracy of the engine, I m sure the_E could detail the reasons better, but so far the best I have been able to tinify things, is to 1/4 size for my star trek mod with fighter-like capital ships.