I personally feel like Saki has a slightly better chance just considering Sakurai’s clear attachment to the series and the character. With KI: Uprising being clearly inspired by S&P, and with Saki being one of the few “irrelevant” assist trophies to return from Brawl to Smash 4. I’m reeaally hoping for Ray as well, but in the light of Isaac and Saki, I’m certainly not giving my hopes up.
As for his design, I’m still of the opinion that Ray should stand at about the same height as most human characters. Like Marth, Link, Samus, and the like. I really don’t feel he needs the gimmick of “really small fighter” to stand out. Being a mech that utilizes all of the various Custom Robo abilities is more than enough. And even though he might be canonically very pixie-like, that shouldn’t really matter. It’s basically the same as Olimar. If they were gonna have a tiny fighter, I feel like it should have been a Pikmin character for sure.
I also would prefer the Battle Revolution model. It’s the game I grew up playing, and it just looks the coolest in my opinion. Also I just like the name Ray 01 a lot, and I really wanna hear the announcer say it for some reason.