Bounty hunter mode sounds suspiciously like the Zombie Riot/Zombie Hell plugin for Counter Strike Source. It's a pretty good idea, but I switched to playing KF almost exclusively BECAUSE it's a perfection IMO of the ZRiot/ZHell idea. Maybe if there is a hardcore flag set that disallows player respawns, it might work.
I have actually never played that mod, or CS:S for longer than 2 hours, so that's actually a coincidence, believe it or not. However, I don't really think a hardcore flag is needed... hell, if a team wipes, that's it. No wave respawn at all like in most other games.
I also wouldn't mind seeing a perspective flip PvP mode where one player controls the Zeds in an RTS style interface while 6-10 survivors try to survive a set amount of time.
A mode like this brings up several questions. Like how would you get resources? How would it differentiate itself from other RTS's? How long will it last? Will this also mean every single community map will have to add in special features so that their map is compatible with this game mode?
In short, it seems like a lot of trouble for a game mode that probably wouldn't fit. As far as "survive as an FPS squad vs an RTS commander" I'm fairly certain Natural Selection already has that covered very well. It sounds nice and simple, but blending different genres of games is very very very hard to pull off well. So, just trying the mode in the first place may very well be a gamble on TWI's part.
A new perk class would be nice too, perhaps one that is focused on building turrets, support structures and traps. Wear light armor that caps at 50, experiences double recoil when firing guns and has their combat knives replaced by a large spanner, but has the same carry limit perks as the support specialist and has the speed bonus perk of the medic. The idea is that those structures are very powerful, but fragile, and needs to be constantly repaired and maintained by the engineer, the engineer also takes slightly more damage and is just as fragile.
I don't think there are many people who ever liked the idea of an Engineer class in KF. Mostly because, no matter what class you're playing you're always shooting something. As though one were personally killing things, on a floor perhaps. Turrets work (somewhat) well in TF2 because they have a counter; the spy and the ubercharge who can absolutely wreck it. However, unless they made a special specimen just for sapping turrets, I don't see this working. Also, chances are the turrets are going to be automatic right?
You will royally piss the hell off any sharp, zerker, or anyone else if they're trying to line up a perfect headshot and/or stun lock a scrake when someone's turret goes "HEY GUYS, I WANNA HELP" and rages the enemy and gets everyone murdered.
So, you'd see the class being used a lot on lower difficulties if it were implemented; because "hurrduurrr it kills for me"
but then it'd become basically a bannable offense on many servers on Suicidal up because your turret would get everyone murdered all the time.
....Also, any resources they have towards making a new class should be spent on making a new Trader menu.