Very good fighter in his prime. He was the 3rd best FW (behind Aldo and Frankie) for years. At 36 and after a long layoff, I don't see him doing well on a comeback. The lighter weight divisions are toughest for older fighters. A slight decline in speed/reflexes can make a big difference.
That said, a lot of people have compared him to Chandler. If Chandler loses to Gaethje and is willing to drop to FW, he and Mendes would be a fun fight. At that point, it would be clear that neither of them is ever winning a UFC belt. But it's probably best if he stays retired and doesn't mess with bareknuckle either. Keep your remaining brain cells, Chad.