Maybe what they could do is do variants on the previous niche repaints.
Paint it in silver instead of gold and you have Hate-Plague Protected Optimus Prime.
MP10-version Ultra Magnus hasn't been done, so why not replace Black/Nemesis Prime with white/Best Friends Forever Optimus Prime! Or alternately, make it all black.
Instead of 7-11 Optimus Prime, they could do a Family Mart one instead.
BAPE has been done, so maybe Angelic Pretty next time.
Instead of Evangelion deco Prime, Death Note Prime. Or better yet, combine 2 renowned unpleasant fanbases and make it Love Live! Prime.