Hm.. A wide and shallow tank seems to be best for partly blind bettas. Dragonscales usually develop scales over their eyes when they're maturing. IMO, I think other fish would stress him out, since he might not know whether they're predators or not. He sure is a beauty, though. (:
I suggest a 2-5 gallon tank. Make it as shallow as possible and more width to it than height. You might also want to try dark colored decorations and maybe some live plants so you won't surprise him. It's up to you, though.