I'd suggest adding some more guidelines to that specific part of the OP, because with abilities like Wonderguard in the pokemon game, the line between okay and overpowered becomes unclear.
I listed a few examples that should have gotten the point across about Abilities already. And Wonder Guard is easy to bypass, as long as it's not something like a Wonder Guard Spiritomb or something crazy like that. It also doesn't prevent stuff like stat decreases and side effects from status effects.
And for your question about the number of Pokemon, like I said, keep three or four on you (I'll let you keep other Pokemon, and you can swap them around and such I guess).
And, since Tyrantrumite is a Custom Mega Stone, it will be near non-existent and unknown to just about everyone. I'm unsure of how exactly to make of it completely based on your description, whether it was found in Viore or created synthetically. That could help a bit.
Other than that it looks good.
@JunkMail
