I just registered on here as I'm the one who has dumped these Hang-On roms and I'm unsure what to do next as regards submitting them to the Mame development team.
I did as you suggested and ran mame64 -romident hangon with my freshly dumped main cpu and sub cpu roms in the hangon folder and it just said "Identifying hangon...." and nothing else so I'm not sure whether the romident function in mame64 for Mac OS X is working as it should do!
I honestly believe these roms to be currently undumped and would love to share them with the rest of the Mame community. The track layout on my version is completely different from the hangon/hangon1 sets. Also, the time you start a race with and the time you get for reaching checkpoints differs from the hangon/hangon1 sets too. The roms all show as "GOOD" when the memory test in the service menu is selected.
Is there somebody that I could email the 6 roms to in order that they can do some further checks on them?