I would be almost tempted to say give KF2 a more RPG like perk system. Like Mass Effect or MAG especially if ever you have played them.
You get so many points and you can spend them on whatever you like, but of course the more sparse your abilities, the more options you have in game, but the less powerful you are with each.
e.g. Points need to be spent on the Medic tree just to be able to use the syringe for example.
e.g. A Berserker style player might be able to invest a large number of points in both damage resistance and armour, but will struggle making up points for damage and/or speed. Meaning he is solid until a FP starts chewing on his face
Of course this is a loose idea with 2 minutes of thought, and I am interested in seeing what your gonna bring to the fray Aze, but personally I'd like to see the perk system expanded into more custom perks allowing the player to define his own roles myself.
Heh, the intention of my ideas is a game which follows the same formula as KF1, but with more weapons etc, AND new gamemodes (like solo campaign, mission maps etc), and new specimen and so on.
However, your little "RPG" style gave me some quick ideas of how it could be done in an RPG/MMO:
3 Kind of classes you can choose from. Let's call them
Soldier,
Survivalist and
Support. (everything is just random names)
Soldier has 3 trees to go into: Commando (about detection and automatic weapons), Sharpshooter (rifles, pistols and stability) and Firebug (fire and aggression)
The Soldier is about surving the specimen apocalypse by using a more offensive style of play. Be it by hunting them down and spraying them with fire or bullets or sniping them from afar.
Survivalist has 3 trees to go into: Berserker (melee stuff and toughness), Medic (healing and survival stuff) and Scavenger (speed and item-finding)
Survivalist is about using things to, well, survive, as good alone as with a team. Be it from running away, medical skills or from fighting with the most common weapons to find: Melee weapons. In essence, it means it's a longlasting class to play.
Support has 3 trees to go into: Engineer (turrets, welding and electronics), Demolitions (explosives) and Defender (shotguns and barricades)
Support is more about surviving the specimen apocalypse by fortification skills (be it mechanical or electronical), and fighting by barricading and killing lots of the specimen at once, with explosives, shotguns or other weapons or traps.
You can basicly also call the Soldier, Survivalist and Support as "Killer, Kiter and Camper" xD
EDIT: Or, if going by more Fantasy RPG names: Ranger, Paladin and Warlock/Mage
But these ideas would all be for a free-roam KF-MMO game
Why not start a new thread about that Jester? Take as many ideas you want from me