Oh, this would probably be one of the greatest games you could port to XBox Live Arcade, but it still needs to be done right (i.e not like Doom was handled). Here are some things that I would need to see improved in the game to warrant my purchase (otherwise, I'll just continue to play it on my PC).
And I agree with the no 3D stuff.

- Full 1080p support (make good use of the Polymost Build update)
- All textures in the game need to be remade in higher resolution
- All the sprites need to be redone in higher resolution (still need big stripper nipples, and don't worry about taking up space. If the game is 300-400 megs, so be it)
- more frames of animation need to be added to any animated texture/sprite (i.e monsters)
- Full proper widescreen support
- Full support for Co-Op over XBox Live, System Link and same system splitscreen
- Full deathmatch support over same services as above
- Add some particle effects to the game (smoke, fire, etc...)
- Add a few extra weapons for some variety (like the ones from the N64 version, grenade Launcher and Plasma Cannon)
- Great, intuitive control schemes (i.e copy the Halo scheme)
- All 3 original episodes plus the 4th episode need to be included
- more maps for multiplayer games (maybe take some classics the community has made too)
- 5.1 surround support

Now, here are some other things I would like to see, but aren't as important to me

- Per-pixel lighting and normal mapping. Would really make this old game shine if done right
- lots of fancy new high definition special effects (weather, bullet trails, sparks etc.... done with particle effects or whatever looks good)
- A new single player episode to play
- Port the "authorized expansion packs" (besides nuclear winter) with the game, either now or later on
- keep the game fresh with expansion pack releases (combination of multiplayer maps and single player episodes) for it (with new achievements to boot)
- new gameplay elements. I kind of liked the idea of saving the women in the N64 version years ago, maybe add something like that to this version. Would make a great achievment if you could find them all
- try and convince Microsoft to increase the amount of achievement points you can get from this game. 200 is fine for games like Pac-Man and Geometry Wars, but for these larger, longer games coming out, we should get more.
- add a few new monsters to the game
- give the strippers more animations. Have them do some other movements, dances as well when you tip them (shake some ass)
- customizable multiplayer skins. Or at least, get to choose some other characters besides normal Duke (like maybe Duke dressed like Uncle Sam, or take some ideas that were used in Duke Nukem: Zero Hour on the N64)

If this game ends up ported in a sloppy manner like Doom was, there is no way I would buy it. If it is done more along the lines of Marathon, then maybe. If it's truly given a next generation coat of paint (don't need 3D models for that), then most definately.