Tower Defence - This could be a awesome multiplayer party game that could have a big modding fanbase for making of different maps.
This can be achieved with maps and mutators. I remember playing on a Tower Defense server that worked quite smoothly. No point making a new game for it..
Hero Siege - Kinda like Dota (I think there is already a mod like this [I should really check the modding section but i'm at work so LISTEN TO ME)) - Where you pick a hero and they have a set of perks and weapons and gain exp and get stronger as waves get stronger.
This sounds like an RPG.. Not a six-man survival horror game.. If they made a Killing Floor 2, one would hope that they stick to what made the first one known, no? Nevertheless, could be done with mods or mutators.
COD5 - Nazi Zombies - When you get higher waves, Zeds can spawn from new location, or new regions open up as you get to higher waves, so when you start only 50% of the map is accessible??
All I got from this is "Add a Fog of War game mode".. Again, maps and mutators.. Noticing a pattern?
MORE ZEDS - RANDOM SPAWNING OF STRONG ZEDS
... That sounds like that one game called Killing Floor.. With a mutator called Faked Players..
(Currently) So at wave 5+ you need a SS for Scrakes and (wave 7) Flesh pounders... well what if a FP is one of 4 different Zeds that spawn??? So Going SS would be strong against a FP but weak against the other 3 zeds that could spawn??? Thus adding more of a random element into the game and more thinking on the fly (so 6 zerkers in hell on earth kiting everything would never happen, you could have a flying zed that needs to be shot at and they would be screwed bahaha)
What do you do as Berserker, take a Katana and a Chainsaw? There's a thing called a Lever Action Rifle, that can be carried by Berserkers.. And here's the best part.. It can shoot at things.. Even if they're in the air!
Single player mode - would be nice, gives a story and can add twists for them who like lore.
Again, taking away from the six-man co-op survival horror.. Which is why we PLAY this one.
Customisable weapons - we want to keep the game hard - but tinkering weapons is always fun
Mods/muts. Seriously, am I the only person here who doesn't have a problem with the current weapons? Sure, it's exciting to unwrap a new toy on the day of an update, but seriously, adding anything else other than what they have will just be fluff.
ADDITIONAL CONTENT - Like with adding themed zeds in here and there, I hope they make it so it's heaps easy down the track to add bonus content
Allow me to direct your attention to:
The Twisted Christmas update
The Summer Sideshow update
The Halloween Sideshow update
Seriously, we're IN an event right now, with real, actual, shootable
themed zombies
I hate to sound like a killjoy, but I mean really.. Tripwire did a fantastic job with Killing Floor, and there isn't much need at all for a sequel..