I think it would be cool if somebody was to make a mod simalar to the zombie mod but say the games could be 30 minutes long but the more you get into the game the harder it gets.
first 5 minutes normal zombies that walk slow average damage
10 minutes crimson head zombies the running zombies with high damage (low amount of them mixed with normal zombies)
15 minutes lickers fast moving average damage (mixed with normal/crimson zombies)
20 minutes hunters fast moving very high damge (only 2-4 ever two minutes still mixed with normal/crimson zombies and lickers)
25 minutes resident evil boss such as the tyrant monster, william birkin or nemesis
Games extras
T-virus cure the infection if bit
First aid spray full heal
these is proberly not possible but we can dream....