I feel like when warhammer 3 comes, there should at least be new units or a new clan that would normally differ from the usual skaven mechanic. Obviously not at the peril of other races but at least have more future skaven dlc if any other race is going to get content also. Unless theres no new content for other races that is.
However clan Moulder is necceasry as its one of the 4 major clans, the thing is, what future skaven units or clans is even remotely important to be in the game now that we already used alot up? unless theres some I don't know already from whats already on the table top.