maybe like Zombie mod for CS:S.....There spawn 2 teams zombies and men. zombies have only a knife, others have whatever they like/can buy. u can stop zombie only if u shoot it in head if i remember good. if u turn ur back at it....it runs faster. and it has health upgrades
so for mta:dm i suggest this:
1 guy is zombie, he chases others on a small area, if u turn ur back at him he run faster, all energy he takes from u, he gets it, so he is more powerfull, he has some health upgrade. when he kills some1, that guy turns to zombie too, and so on, until every1 is zombie. but there should be some time limit, like 10 mins....if every1 is zombie before that - zombies won, other way - they lost;
or there could be 2 teams (16-16). every dead zombie becames a human, and every dead human becames a zombie, except for suicides - that way, if u died like a man, u spawn like a man
I have tried to script some stump to Zombie mod for mta.. I dont just know Lua so mutch. ^^And i got 2 maps too ready. =D