Doesn't exist
So how game gives movesets to random characters? Some grabs are added automatically from mods, but restraints for which you has spent a lot of work and time just not used in exhibitions by enemies and they can only be added manually in H-labs.
Is there a file like unitdatas_versus_mode.json for random characters? Random sets of grabs are taken from old grabs base - so I presume there are a file with this base.
Game iterates over all defined grabs, filters them, and selects 8 at random. The randomly generated characters are currently excluded from generating RESTRAINT grabs.
unitdatas_versus_mode.json is not used for random characters. Character randomization is not configurable by json. You might be thinking of random_char_cards, which is used to help generate more handcrafted outfit sets. There is no equivalent of random_char_cards for random grabs.