ns_ mvm and co_ mvm are two different things. I don't know the exact reason why co mvm does not work anymore in b5, but I guess that it is because alot of the offsets have changed in b5 and the plugins which where required to run co mvm properly don't work anymore. So they would need to be updated. But since I don't care about co mvm pretty much, I'm not sure about it.
as for NS mvm.. only with work from the mapping point of view you won't get to work properly. Since I'm working with somone on a plugin to get NS mvm to work for about 2 month by now, I can tell you, that it's not easy.
Some of the problems of ns mvm are:
- you don't spawn at the info team starts, instead you stay in the readyroom
- if team 3 is completely dead, the other side wins
- you can't have any rt's because the engine can't handle two teams with each marine resnodes (the reason why you crashed)
- team 2 commander can't drop or build anything
etc..
and these are not things you can fix by only mapping. But feel free to try

and no.. ns ava does not work properly either .