Rename mob's tool

[FistoF]

Is there a way to change the name of a naturally spawned mob's weapon?

I'm needing this so I can use it along with OptiFine's item name-based texture feature.

E: I'm going to try:

set main hand tool of last spawned pillager to crossbow named "Rifle"

 

[Shadow501pl]

set last spawned entity held item to crossbow named "&aRifle" with lore "" and "&a&lUNCOMMON"

Do this:
on spawn of pillager:
#code