He can probably do it, but ideally you want to fill up every ounce of your weight class. It would be really difficult and time consuming to put on an additional 10lbs of muscle mass, for a 145lb guy, while remaining natural.
Thats what around ~107% of his total current mass?
Some fighters do it, like BJ Penn just being an outstanding fighter and being able to dominate multiple classes. Randy Couture going from 205 to heavyweight, Dan Henderson going from 185 to 205, etc.
I think that he should be scared of physically stronger fighters in the 155lb division, for example sherk, and also more technical fighters that fill up the full 155lbs like BJ Penn. Unfortunately I think he would have his ass handed to him by those fighters. He tries high flying techniques that are exciting but I've seen him carelessly give up certain positions, like his back, against a bjj black belt that had 20+ fights. He's just been able to physically outclass his opponents through his strength and conditioning. He won't be able to do that in a heavier division.