Hello
I'm thinking from a machines/dataset poit of view, if I understand:
HBMAME - ROM hacks and stuff not permitted for MAME - Conatins some machines in MAME but mainly just the parents for the many clones.
ARCADE64 - A subset of MAME with the machines you personally like, with a nice UI.
Seems to me they are different animals. If it makes your life easy then go for the merge.
I personally would like to see the 2 datasets seperate. But as a previous poster says if there was a flag to filter HBMAME from standard MAME stuff I'd be happy.
Cheers
Sam