AFAIK It's very rare in 2ch/pinkbbs to merge unsuccessful boards once created.
If possible, I recommend to merge wildplus, femnewsplus, dqnplus and ticketplus into one "socialplus" board. They all lack both reporters and residents, and there's no PLUS board that corresponds to socio-news. (we already have political, economic, international, scientific and sport/entertainment ones. Only social one is missing.)
Usually we don't merge boards b/c usually a few (very few, but not zero) residents do exist in any board and there's no harm in keeping unpopulated boards.
I recommend to merge some PLUS boards b/c they need volunteers (CAP) to work correctly, unlike other normal boards.