Every time I try to comment on XL2 / ZT technical information, I'm embarrassed by being incorrect. I will say this however, not for anyone, just an estimation.
- Expanding the game world to be more open [read: more polygons in the level geometry, farther view distance, more free camera] like SM64 entirely axes the possibility of 2-player. Is that important? Not my choice.
- Expanding the game world to be more open like SM64 carries technical possibility, but I think it would increase the texture warping and it would likely come with a decrease in apparent world texture resolution.
(the above based on the assumption that the polygons of world geometry become 'larger' in size to fit the scene into the polygon limit)
- XL2 might be facing memory limitations combined with polygon/sprite/view culling complications. These become worse with more things being potentially visible at once. Solving one or the other could be done with file system usage (reading visibility data based on sector or loading assets over other assets based on sector); combining the two into a unified solution would take a lot of time.
- Looking at Ninpen Manmaru however, I think there is definitely room to move the levels to be like that. But those levels are very very small.
- The big and VERY impressive push we're seeing is probably a build-up to SAGE, after which I imagine he might have more time to look at bigger changes.
Thanks again to XL2 to providing his technical expertise.