So here's my idea.  You have an infected that can have two special infected skill sets.  Obviously it can't be TOO cheap (i.e. hunter + tank, jockey + boomer), but they can do a little toggling.
 
Maybe if you take this route, your attacks/reaction times/etc. are lesser than if you specialize in just one.  Also, it'd be pretty funny watching a Spitter animating to plump up into a Boomer or a Jockey roiding up to a Tank.

L4D3 needs more Bill.

I'm sick of this series.  Hopefully they have all been Left 4 Dead 4 Good.

" i have an awesome left 4 dead 3 zombie idea and i really think valve would use it so im not gonna tell anyone about it (i really want to though but im afraid someone will steal it) "

" L4D3 needs more Bill. "

" @creamypies said:

" L4D3 needs more Bill. "

I don't understand why people like Bill so much. He was the worst character in Left 4 Dead 1. "

" @natetodamax said:

" @creamypies said:

" L4D3 needs more Bill. "

I don't understand why people like Bill so much. He was the worst character in Left 4 Dead 1. "

:O BEST CHARACTER ! "

" @ZombieHunter said:

" @natetodamax said:

" @creamypies said:

" L4D3 needs more Bill. "

I don't understand why people like Bill so much. He was the worst character in Left 4 Dead 1. "

:O BEST CHARACTER ! "

All I remember of Bill is him saying "Ooooooh Louis". I remember nothing else, and I just got done playing the game a few hours ago. I remember Francis and his constant hate of everything, I remember Louis because PILLS HERE, I remember Zoey because she's friggin Zoey, I remember Bill because...........old guy? "

" @natetodamax said:

" @ZombieHunter said:

" @natetodamax said:

" @creamypies said:

" L4D3 needs more Bill. "

I don't understand why people like Bill so much. He was the worst character in Left 4 Dead 1. "

:O BEST CHARACTER ! "

All I remember of Bill is him saying "Ooooooh Louis". I remember nothing else, and I just got done playing the game a few hours ago. I remember Francis and his constant hate of everything, I remember Louis because PILLS HERE, I remember Zoey because she's friggin Zoey, I remember Bill because...........old guy? "

 also it appears you only remember zoey because shes a girl and louis because hes a funny black man  "

So you're saying Left 4 Dead should have dual-classing.  
 
I'd agree that the infected could use some more player-customization.  Maybe some feats or prestige classes.

" @creamypies said:

" L4D3 needs more Bill. "

I don't understand why people like Bill so much. He was the worst character in Left 4 Dead 1. "

I'm not really yearning for another. At least not anytime soon.

" L4D3 needs more Bill. "

" @creamypies said:

" L4D3 needs more Bill. "

Bill's dead. "

" @creamypies said:

" L4D3 needs more Bill. "

Bill's dead. "

This is an interesting idea. 
 
Let me throw out one of my own... How about if there was a 'Chameleon' infected that would take the appearance of one of your teammates, with the player's name floating over their head and everything, but their face or clothes were messed up so you could identify them on closer inspection? They could sneak into the group during hectic fights or when players get separated, it would really start to make people paranoid.

" @systech said:

" @creamypies said:

" L4D3 needs more Bill. "

Bill's dead. "

That's the joke. "

They should combine some, Left4Dead 3 can't really have 10 infected types.

Chicago Ted

In Left 4 Dead 3 I wanna play as the Midnight Riders, baby! I call Ox! :D

In Left 4 Dead 3, I want to play as a paraplegic, because the survivors are slightly overpowered in L4D2.

That's a good idea. I just want more infected types.

I have a good idea. How about they stop making sequels and just do DLC like they've been doing for 10 years on their other games?
 
Yeah, and it's free. PC FTW