This is a really weird way of tackling the issue...which is that the challenge system is completely nuts. 10k hip fire damage? Really? LMGs aren't supposed to be in CQC...their bloom and recoil is off the charts...hip fire only works in panic situations or vs bots...
Personally I would have brough back solo/co-op vs AI with full progression and clamped down on AFK/XP farm lobbies by not making them possible...I mean literally, if you join any of these maps they're purposely bugged so there's no ticket count and some of them turn into a bunch of dudes spawn camping and blasting the crap out of a single area until time limit hits.
These kinds of maps should be easy to clamp down on with minimal collateral damage.