Wither skeletons should attack players with piglin/brute identity
Wither skeleton identity should inflict wither upon attack (and maybe be immune to wither)
Piglins should run from zombified piglin/zoglin identity

Alright, I already added your ideas:

• Wither Skeletons attack Piglins (as of 2a8ee07)
• Piglins run from Zombified Piglins and Zoglins (as of f85f494)
• Wither Skeletons inflict Wither Effect (as of 972eb25)

I'll do my best to implement this :D