ROMVault I did look at as well because I think that DOES do a whole big DB with all rom collections, doesn't it?
Yes, ROMVault does. As much as you want to put into it. It gets unwieldy if you put all you can. What I do is put the all the pinball stuff in one instance, the MAME, FBA, HBMAME, MAME rollback, RAINE, Winkawaks, etc... stuff in another, the no-intro in another, Gruby's SCUMMVM in another, and tosec in another. I don't know how well it handles the good/non-good collections, I haven't tried them.
Having separate instances of ROMVault is useful when you have new MAME ROMs to archive, and you don't want to waste time re-scanning the pinball collection. The checkmarks on the DirTree can be used to isolate the part of the db you are using, but having a huge db makes the startup and db-backup phases take too long.
There is a little overlap between the MAME Software Lists and no-intro, instead of combining them into one bigger db, I make a fixdat on one, then fix it on the other, first "pointing" the output to the first one's ToSort folder.
How long ago did you look at ROMVault? It's up to v2.2.7 now, and a 2.5.1 beta release is pending. Looks like some form of .7z support will be in the 2.5 release. No eta on header skipping yet.