This depends on two things:
1) What his wage demands would be. After thirteen years of careful wage control, I'm sure no-one at the club wants things to slip between their knuckles for the a short-term replacement who's best days are behind him.
2) Whether I could cope belonging to a fanbase that might start pouring in with people who unironically think Ronaldo is better than Messi. Like people who think the American remake of The Office is superior to the original, although they may be legion, it's best to keep them out of your life for the sake of your mental health and quality of existence. If it turns out to be too irritating, I'll be using my direct line to the Sheikh to get him sold back to Serie A for a lark.