Thank you, mister burch, for acknowledging my presence. It makes me feel warm and happy. Anyways, to counter your point, my freeform simulation using the Quake engine currently uses a map like a stack of very large, very thin, very hollow pancake-like spaces for loading planets, ships, etc, in a not totaly unlike EV way. Well, almost, since there isn't all that much actually done yet. One problem with the engine is size of systems...
Although the BSP format doesn't have any real size limits, by default the engine reads and writes points using integer types (longs, but I'll have to check that). The resulting maximums are +-4096 units (a ship is about 16-32), which is crap (I guess you know how big EV's systems have to be). With the source, and two (yes 2) lines of code changed, it uses floats and the map can be bigger... by several orders of magnitude. I could also give up on using this BSP-based system at all, and just have 3d space (by not loading the map), but that would limit the number of active "areas" (systems, atmosphere, and anything else that I might want to include) to 1. The rendering speed increases by about 3 times, though, so it might be the best option.
If you want some good reading, code, a forum for intellectual debate, and some links to other good resources for game design, go to idevgames.com
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-- Nikolaus Wegner