For starters.
1. Other locations.
2. larger more indepth maps.
3. Female characters and voices.
4. Ethnicly divers characters.
5. Improved AI ( no more funneling/Kiting the zeds).
5. New specimens, especially zeds with ranged attack/weapons, and faster movement.
6. New classes and levels.
7. More/different weapons.
But thats based on visual representation only, it doesn't directly effect gameplay for the majority.
1. Other locations - Simply new maps, can already be done with the KF we have now
2. Larger Indepth maps - Same as point 1, can already be done, they're just new maps
3. Female Characters - I can't see how this would change gameplay, and again can already be done with KF now
4. Ethnicly divers characters - How would that work? How would that possibly change KF gameplay, its just visual representation
5. Improved AI - I can see how improved AI could improve gameplay, but again its not something that calls for a brand new game, you can pretty much tweak the AI in what we have to your liking, but better yet, to what extent would you tweak the AI, its already up on its limits, we've seen teleportation, the only thing left would be ghosts, which I'm sure could be done by the correct modder.
5.2 New specimens - That one I can get on board with, but not for an entirely new game, they could add some new specimens into what we have now, hell there are tons of modded specimens, they just need to be made official.
6. New classes and levels - Again something that can be done in what we have, and I can't see how many more classes we could fit in that would actually make for a good game, I've played modded servers with new classes, I gotta say, they aint all that, it just becomes a confusion fest.
7. More/different weapons - Again modders are doing this nonestop for KF, its not nearly good enough to base a new game on.
With that being said, a combined effort of many of those things could create a KF2, but it wouldn't be worth it as it wouldn't be opening any new doors, it would be KF1.2 now KF2.
I appreciate the ideas though wasted, keep um coming, you never know TWI might just be watching in the shadows for that extra special golden nugget to fall, you could be the person to drop it.