Count me in as a supporter! I loved the idea back in the Brawl days and I still love it now. However, I don't think the Hanafuda cards should be in their box - Mr. Hanafuda/Hanafuda-Man should be an open deck of Hanafuda cards (still with arms and legs I guess, for movement purposes), allowing you to see the front card of the deck (the cards are somehow held together by magic
). From there they could implement some kind of shuffle mechanic, where the front card of the deck somehow dictates the strength or effect of a move.
I haven't really thought the mechanic through thoroughly, mostly because I don't 100% get Hanafuda, but what I envisioned is that when performing a Smash attack with Mr. Hanafuda, he would do a Smash attack and 're-shuffle' at the same time, putting a new random card on the front of the deck. The card on the front of the deck would then influence the strength and attack-effect of the next Smash attack he performs - regular flower cards would be bog-standard Smash attacks, Ribbon Cards would have a slightly stronger effect on Smash attacks, and cards with characters on them would do the most damage/knockback, and/or have an effect applied to them (freeze, fire, aura, Ganon's dark energy, electricity, paralysis etc.) depending on which character card is pulled.
Also, to make the uninformed a little more comfortable with an idea as alien as Hanafuda Man, I wouldn't be against them opting away from using traditional Hanafuda cards and choosing the Club Nintendo Hanafuda cards instead:
Just my two cents.