I'm not saying all abilities are off limits period (we're not permanerfing him), but Diabound would be the very first Really Big Summony Thing we have in-game, by my count. There's a lot of room to get reckless with that, and while it's not that I don't trust you, again, we do need to keep all characters on a relatively similar playing field here. I can understand wanting to get Bakura more involved, but he was... well, a noncombatant within his own canon, and it's not as if characters sans fighting abilities can't get a piece of the plotty action, too.

Therefore, I'm still going to have to say no on granting it any additional abilities for the time being beyond just showing up. Because... going through walls is still kinda gonna cause some panic, which ties into the first concern. This would make ten Echoes for you with these two included, so I believe this is a reasonable compromise.