If TF2 were to have a Zombie mode.
If Valve were to do a zombie mode for TF2 (similar to Mann vs. Machine), here's what I think it'll have:
BLU: Surviviors (players), cannot respawn
RED: Zombies (bots), can spawn almost anywhere
Scout - 1.5x faster than human version, most common zombie, but also the weakest (has 1/3 health to its human counterpart)
Solder - able to super jump (rocket jumping without the rocket launcher, similar to vs Saxton Hale mode), and spits out exploding organs (blast radius depending on how large the organ is)
Pyro - Almost immune to fire, can spit burning acid at players, cannot run after it spits the acid
Demoman - Can do a kamikaze style attack that deals a huge ammount of damage to anyone within the blast radius, but also kills nearby zombies, does a smaller explosion when killed (one of the most dangerous zombies in the game mode)
Heavy - 2.5x more health than human version, slowest zombie, 2nd least common zombie
Engineer - can create a bonewall which hinders the Survivors' ability to advance (or retreat, depending on the mission) which can be destroyed by attacking the wall, or killing the zombie Engineer, and zombie Engineer loses speed by creating the wall
Sniper - has two unique attacks, a long tongue which snatches a survivor and brings him to danger, but exposes its position and leaves itself open (similar to the Smoker from L4D), and spits out a tooth which damages (but not a lot) a survivor, and marks him for death (similar to the Fan o' war, and Jarate).
Medic - has an aura around him which heals surrounding zombies, and damages surrounding survivors, cannot auto-regen (unlike its human counterpart)
Spy - is cloaked (albeit, in a dark mist which makes him slightly visible), and only decloaks before it attacks, decloak sound is heavilly audible, uses a necksnap (zombie version of the backstab, and is also heavilly audible), least common zombie
All - use a melee attack when close, bites a survivors neck for an insta-kill if the survivor is heavilly surrounded, if the crit will kill the survivor, and/or if the survivor has very low health, heals by feasting on the corpse of a fallen survivor, (except for the heavy and scout) has 2/3 health to their human counterparts
Missions (the ones I can come up with, anyways):
Scavenge - Survivors must grab a set number of supplies and must bring those supplies back to base.
Supply grab - Similar to Payload, Survivors must bring a cart full of supplies back to base, mission does not start until the cart starts heading back to base, recommended that a few stay in base to cover those bringing the cart in.
Onslaught - Survivors must hold off a set number of zombies, or hold them off for a set time limit
Rescue - Survivors must go through multiple points in order to get to a rescue zone.
All-out assault - Similar to rescue, Survivors must rush to an Attack point (to a total of three), which is heavily defended by zombies, each attack point captured kills every zombie surrounding the area.
I want to hear your opinions on this, and how this could be improved.