a silly thought just came to me, to become a completionist you have to go through every class and once you tr for the final time you have to use up a feat slot to gain your +2 to all stats.
it would be the most challenging class to get to 20 and tr but if you do you would get a +1 to all stat auto grant past life bonus (can be stacked 3 times) and access to the current +2 all stat completionist feat

completionist class:
+1 all saves/3levels
no armor proficiencies
simple or no weapon proficiencies
no enhancements (only racial)
no class skills
no spells

so what do ya think?