First of all Welcome ST!!
I agree with M4M that it would be easier to replace someone like AJ than Carmella. I think I could adapt to a different AJ, since his role is not that significant as of yet.
However, I don't know why they'd replace him. We are all use to him and he isn't a bad actor. If they decided to make a swith with AJ, it wouldn't bother me. if they ever replaced Tony,however, that would be a different story .Then show would go down the tubes as far as I'm concerned.
TIS