Retrofitting non-functional Manta V1

So i have the opportunity to pickup a nonfunctional Manta system that buddy got during the crowdfunding program. Batteries are dead.
Anyone have any thoughts or experience retro-fitting this system?
Im currently utilizing a 6384 with a Max5 Speed controller in a backpack with a 12s3p battery with success. The fabricator in me thinks an under the board FD2 style system with no cables would be rad(er).