I'm much more experienced in the system today than I was when I first posted this to the now-defunct pathfinder.social instance. But I've only had experience behind the screen, so I still don't have the hands-on player-side experience to give a fully-informed take.
My feeling is that Charisma is already useful enough; I wouldn't want it to take over Will saves from Wisdom, which apart from Perception (including Initiative) feels like a relatively under-utilised ability.
The Strength and Constitution merger seems like a really good one.
I'm largely undecided on dex. The fact that by splitting them you are also allowing the new Dexterity to apply damage on finesse attacks is really cool. I like how that sort of offsets the inherit nerf dex is getting by being split, so it's nerfed a little less in these specific ways. But now the typical rogue has three abilities that they really rely on in combat (dex, agi, str) instead of just two (dex, con). (Or 4 instead of 3, if you want to add wis for perception.) Not to mention now the thief racket loses their main bonus.