NOTE: Before anyone gets the idea that I'm trying to say, "Hey! I've got a cool idea! Who wants to do it?" let me just say that I want to make this idea...I just need for some other things to get sorted out first before I even begin. Also, if I never get around to doing it, I don't want the idea to simply die out.

What about a Duke mod? Duke's got an interesting personality, for one thing, and any conversations during the game are sure to be fun watching. Also, it would interesting to not only see Duke's world open up in a more dramatic light than the killfest that was Duke 3D (never mind DN: Forever, which is taking that long to get here).
Points in mind:
1. Dancers. Duke had them first, Deus Ex perfected them. Half of Duke's levels are bars, anyway.
2. Weaponry. Much of Duke's weapons and his usage of them could benefit greatly from the RPG system. Finally, you have the ability to disable Tripbombs when you come across them! Only thing is, I don't think Duke would go for a sniper rifle, so that (might) be ditched.
3. Enemies. Let's face it, Duke's enemies were dumb. Maybe in this he could face those white aliens from Deus Ex as the bad guys. If anyone figures out how to add pig cops, too, that would be a bonus. Sneaking for Duke might also be an interesting option.
4. Atmosphere. The Deus Ex atmosphere is perfect for Duke's world. Dark, disturbing...and with the capabilities for being humorous in the wrong hands, namely mine.

Only two bad points:
1. Copyright. Maybe if it was worked off as a parody, or 3D Realms doesn't care, then maybe there would be a chance.

2. Inventory. Obviously a good, manageable inventory is key, and the limited space for Deus Ex wouldn't work all that well...unless each weapon only took one space, allowing room for other inventory objects. Actually, this might be good...finally, Duke will have to think a bit about what stays and what goes. If Duke's good with RPGs, for instance (from upgrading Heavy weapons), he might not want the pistol anymore. Of course, if he wants to be a bit more silent (or have a weapon that stores more ammo), he might drop it in lieu of the pistol. You know, exactly like Deus Ex, except with Duke.

Personally, I'd just like to see Duke may the leap to the true 3D arena for the PC, and if 3D Realms is still working on their version, why not create one while we're waiting?

I'm also going to post this in The Editor's Guild, since many that frequent there might be interested.