Have you seen Snake?
Dude's a monster. IMO he has a few clear weaknesses, but definitely has the tools to work around them. He never wants to be in the air unless its on his own terms - he's huge juggle bait and has trouble getting back to the ground, but with smart use of grenades, C4, Up B, wavebouncing and good ol' airdodge he can make something work. His recovery just leaves him wide open and it's a little awkward to sweetspot, but proper survival DI, grenade recovery and C4 recovery he just keeps coming back. He'll take a lot of % getting back on stage, be it from edgeguard attempts or himself, but always eventually gets back on stage where he's comfortable. Even with his reduced weight (and let's be honest, his Brawl weight is just silly for a regular sized human) he tanks stocks incredibly well. His other weakness imo is his lack of real approach options. But in that regard I liken Snake to Sheik. Sheik's approach is pretty garbage too, but they both have excellent spacial control. So rather than directly approach they just sit around medium-close range and limit your options and play a more reactive game; he has the tools to stuff your approach and convert it into a positive situation for himself.
So he can definitely work around his weaknesses, and play to his strengths very well. If you ask me, he's one of the most well designed characters in this game.
ZSS, I have no experience with so I can't say. Looking at her as somebody with no experience though, she seems like a sortaFalcon that doesn't get ***** for being a fastfaller, so that's bound to be good. Kind of like how 2.5 Sonic was a sortaSpacie who didn't get ***** for being a spacie, but her design doesn't seem to have toxic elements to it.
In all seriousness about Meta Knight, I think SB's placement for him is about right give or take a spot or two.
Funny note, for the first day of playing him I kept using Dair thinking I had Brawl Dair. Brawl Dair is like free edgeguard mode... Using PM Dair thinking it's Brawl Dair is like free killyourself mode