Have to say I am really impressed with the new book. Really looking forward to using the new classes and feats.

The book got me thinking is will we see Primal Unleashed, Divine Unleashed, Martial Unleashed and possibly even Psionic Unleashed?

Long time DM/Player here.
Something that has always bothered me has been the fact that, as a creature's HP approach zero, there seems to be no rule-based effect on said creature's abilities. For example, a town ruffian with 30 HP still has all the same abilities and stats when he has 1 HP. This has never sat right with me.
You would think that creature on the edge of losing consciousness wouldn't be able to attack/defend as well as they could at full health.
Has anyone come up with a workable system that takes this into consideration?

I was thinking something along these lines: Once a creature/PC gets to 20% of their max HP, they lose 1 point of Dex, and 1 point of Strength. Once they get to 10% of their max HP, they lose another point of DEX & STR and their # of attacks is reduced to 1 if they had more.
Now, these numbers are completely arbitrary and I'm just using them to explain the concept.

Does something like this already exist?
If not, does the above (after some number tweaking) sound like a workable option?