A simple solution might be that getting tadpole'd or having a prism guardian grants our characters some additional feats from the standard list. Or maybe the Tadpole boon is just to get a free ASI somewhere, so it's not tipping the scales so hard. If the standard feats were based on our XP this would also allow them to keep it going past the current lvl cap, and provide a campaign specific conceit for spiking the brew that way.
The benefit there might extend to Multi-classing too which already takes a hit due to the ASI nerf, unless you take a second class at the natural breakpoints for that (every 4 lvls), which is pretty limiting here since they capped it at 12. Means most wouldn't even consider flavor feats probably, or take them late which isn't as fun.
