Topic
the rule that I know is that if the character is on your team, you can't include any of that character's cards under your Battlesite.
(tournament players may have a better feel for the legality of what you are proposing.) even though it would be a card in your deck and not your Battlesite, I would say no without an explanation of why it should be allowed.
If Beyonder is on your team. You can not have him as an activator in your deck.