Do a 3D accelerated version. On modern hardware (fast pentium + 3DFX)
you probably wouldn't even need to be clever -- you could just draw the
entire level and get reasonable speed. With a touch of effort, it should
easily lock at 60 fps (well, there are some issues with DOOM's 35 hz
timebase...). The biggest issues would probably be the non-power of two
texture sizes and the walls composed of multiple textures.
I don't have a real good guess at how many people are going to be
playing with this, but if significant projects are undertaken, it would
be cool to see a level of community cooperation. I know that most early
projects are going to be rough hacks done in isolation, but I would be
very pleased to see a coordinated 'net release of an improved, backwards
compatable version of DOOM on multiple platforms next year.