Scrakes and Fleshpounds shouldn't be a problem, they should be dealt with promptly by others in the team.
Even if the zerker dies half way through a wave, the team should have saved plenty of ammo to not have to worry making it to the end.
It's even easier if you have IJC whitelisted weapons, so the medic carries 3 medic guns and the Sharp has an M99 AMR.
Well places pipes just inside the door (protected from sirens) can deal with Fleshpounds, and the zerker just needs to drop back and someone make it rage whilst the pipe goes off. A good zerker won't take a hit from the Fleshpound if he has a good team behind him to remove it quickly.