
You'd have to then truncate the long filenames, cook up a make file, etc. but it's still very possible to get it into DOS no matter how advanced the engine is. Hexen II's best port had a DOS version (H2 never was a DOS game)
If you do make Dreamcast hardware support in there (SGL api) you could hack in PowerVR PCX-2 support as well even though no one uses that card but me! But if you get one of those crappy cards (Apocalypse 3Dx) and optimize for that, it'll benefit the Dreamcast as well since the chip in that is a direct successor with the same features, plus blending. Good luck turning leafs into infinite planes, though... also remember, vertex lighting will help a ****lot**** for this chipset, so you'll also have to come up with a good implementation to translate lightmap to vertex.
Forget about ADX and MP3 streaming, that's very very patented.