He can't, and he wouldn't (even if he could boil himself - in fact that would almost guarantee he gets KTFO)
Not a fight that I would want to see. Josh Taylor would win by KO at 140 or any catch-weight up to 147 and beyond. Pac-Man, he still has some fight in him, but he is 41 years old. That is too far a disadvantage to overcome against someone like Josh Taylor.
Tbh, the thought of Pax getting back down to 140 didn't sit right with me so much that I assumed this meant a prime Pac vs Josh when I read the thread title.