Why you don't let me put addons on left 4 dead 2

So L4D2 went free on christmas so naturally,I snagged it up.  Then the addons happened.  To give an idea of what's going on here, we have our survivors replaced by Deadpool, Isaac Clarke, Master Chief, and Princess Celestia.  For the weapons, I won't even go into all of the addons I use but here are some of my favorites.  The pistols are now halo 2 pistols complete with sound effects, the magnum is a Dead Space 2 Plasma Cutter, the fireaxe is a gravity hammer (With sound effects) and the machete is an Elite Energy Sword...  I used the DEV console to spend some time in third person but it comes with some really annoying aiming issues with the reticle.  Anyway just posting to warn you that addons can be horribly addicting.  Later I'll post my Gen 1 survivor team who's just as outlandish in look