About the Cresselia well yea you said it, Tyranitar completely destroys it and is the second most common pokemon. Scizor of course can also do a ton of damage to it and it is the most common pokemon. Im not saying it couldn't work though, all that would really be needed is some lures, like Life Orb Celebi, or Choice Specs Latias something like that and maybe dual screens, overall pretty interesting idea I think