VMware vCenter/ESXi with FreeIPA instead of Active Directory?

The VMware vCenter appliance (SuSE Linux-based) uses Likewise (open?) for Active Directory authentication. See the notes on joining AD here.

That would be your starting point; examining interoperability between Likewise and FreeIPA...

I've just went through coupling Vcenter 5.5 and FreeIPA. You can add it as OpenLDAP identity source and add individual users to a vcenter roles. unfortunately I couldn't operate groups, can't even see them in the list.