I actually like the second set of ideas more with DFF and Persona - the first set is more of the kind of thing we'd do in assemble. Deckmaker-made-specials should be on a more specific theme like a specific series and such. Things that are too organized for an assemble to make sense with. I'll add protagonists/antagonists to the assemble ideas list though.

So yeah, totally go for it with the Dissidia and SMT ones. I don't know a ton about either of those fandoms (sans Persona 4) so I'll leave how to handle those up to you. Whatever size you want and all that jazz. :)