I'll start with a few points.
1. Even 5e has proper multiclassing. PF2 should have more customisation than 5e.
A lot of possible builds in core PF1 simply do not exist in PF2 as is. That is what I dislike.
There should be, simply, a list of generic class feats that ANY class can take, that lets them access what should not be a class feature. Like dual-wielding weapons. Being competent with a crossbow. Being competent with a ranged weapon. All this stuff was possible in PF1, but are now locked behind class feats for no real reason.
Also, restricting multiclassing to only 'class feats' feels likes scrapping a core part of PF1. Even 5e allows multiclassing, why can't PF2?
Species is a more accurate term.
Hell, you could have a new acronym to represent Pathfinder Society, replacing the 'ABC' backronym.
Profession (replacing class)
Personally, I'll just be using the word race whenever 'ancestry' pops up in the rulebook. One syllable is faster than three. Besides, changing one word is simply, well, not useful in its desired intent.
Do you know of any third-party/homebrew classes that meet those requirements?
I actually wrote one a while ago, but I'm not sure how balanced it is. I'd link to it here.
(I read through the rules, and it seems like I can link off-site to other forums, or at least it didn't say I cannot. So I did. I'd reformat it here, but Paizo messageboards don't have table formatting.)