As for variety of characters, there's only about two types of enemies so far per map. I don't want to go over three different types for later levels. Although, there's an average of 10 to 12 enemies on each one. And I'm kinda going by the half life style of weapon selection, so in the 9 levels I have so far the player has three weapon (Colt, Uzi, and Mossberg).
If you can spare some time, I can send you a zipped folder of the build game I have so far.
"I think I'm getting the 'Black Lung,' pop."
"Derrick, you've been down there for one day."