L4D1 only has a limited amount of game modes, which is a total of 4, namely "coop","teamversus","versus", and "survival". It does not have the mutation system that L4D2 has.
If in case you(or anyone else) would like to try making an L4D1 version of your implementation, you can also use the
L4D CVar Reference and look for the
sv_gametypes or
mp_gamemode cvar. Nice work btw
