I'll like to make a few things clear.
1.) Before my main post, if someone comes in here with different opinions on Geno, I feel like thats perfectly acceptable, as long as if they aren't bashing or they're acting like a victim whenever they make a bad post and get called out, discussion is perfectly fine.
2.) Don't act surprised if you have different opinions on the character and you get posts disagreeing with your opinion, this is the support thread for a reason.
With that out of the way...
There is no "Deluxe Mii", nor any "special treatment" any characters get.
These "Deluxe Miis", are just a special ways to represent requested Indies in a way that wont sting like spirits, they aren't replacements for any character, they're just a way to give indies better representation because Nintendo/Sakurai, isn't fully ready to make one a legit fighter, but still wants to deliver to the fans who wants it.
Geno, will not get this "treatment", its a matter of opinion if you believe it'll suit him better, but, to me, Mii's doesn't represent Geno well in the slightest, it only shows that he can shoot things when that's far the only thing he can do, and Sakurai is aware of this. The reasons why Sakurai added the Mii in Sm4sh is to achieve something close to a fighter, to semi-fill the "want" in the fans, and Sakurai himself.
Geno was already a Mii in Sm4sh to begin with, which almost completely rules him out at being a upgraded Mii Costume, there would be no reason to do so because, they could just achieve the idea to please Sakurai, and a lot of fans, by finally adding him in.