If you want crunch, the Pathfinder2 is your game.
There is potential for the shifters/weretouched, but these can't be only the same Stacey Malibu doll but with now with a new and different hat. Each PC race is like an urban tribe, with their own marks of identity. And the subraces haven't explored enoughly. We need ideas, as an alternate origin, for example a shifter was created when a primal spellcaster (druid, shaman or ranger) used her animal companion as an emergency plan B if a reincarnation spell was necessary, or caused by a not-totally-succesful exorcism to heal a theriantrope curse. Or the curse was intentional to avoid be infected by ghoul bites. Why not a racial feat like the "second skin" dark gift from Ravenloft 5th Ed? Do you remember the huargen, the playable race from World of Warcraft?
The shifters could be a common race in the armies of Vodoni empire (a Spelljammer faction).
If the shifters have lived in their own tribes...how could they be hidden in the same forests than elves, orcs, gnolls, bugbears and other savage humanoids? If they are born among the members of other race, how would be a shifter born among elves or orcs?
Are shifters with werefox ancestors be possible? These could be interesting tricker characters. The Wildhunt Shifting Feature could be useful for spellcasters shifters (let's imagine a player who loves monster girls-kemonomimi waifus + maho shojo/magical girls). (I mean the design of the new PC races should to avoid the typecasting)
Vicent, played by Ron Pelman from 90's TV show "Beauty and Beast" can be a good example of shifters as an interesting character.
What is the link between shifters and hengeyokai as PC races? They share some common points.
Could thi-keen become weremantis?