Here is my unpopular opinion: I don't want Aaron to do anything in Better Call Saul unless it's a simple one-time cameo for fans that's set in one of those flash forward teasers.
Furthermore, while I think that Better Call Saul is done well, and has a likable cast, it is not, nor will it ever be, as great as Breaking Bad. I think BrBa fans are still in their post-mourning phase and want BCS so badly to fill that hole the show left that they are praising the shit out of something that's merely a good show.
It took me until 'Alpine Shepherd Boy' to even give a shit about any of the characters and that's because I was worried about Chuck. I love Bob Odenkirk to death, but I don't think he really can carry a show on his own. He's been trained to work with an ensemble, he's been doing it his entire career. The one major thing that Breaking Bad had that Better Call Saul doesn't is an acting force that rivals most Oscar performances. And yes, I know that Jonathan Banks is in this cast, and yes, he did an amazing job in 'Five-O', but that episode was an anomaly, a gift to an actor that Vince and his team love. But Mike's story is not what the show is about. The only reason I'll keep watching BCS is because of that one hopeful day that they bring Gus Fring back, because that was a secondary character that was worth finding more about. But Breaking Bad is over, Better Call Saul will never be another Breaking Bad, and the major cast of players from the latter show should move on with their lives just like the rest of us.
I'm getting really tired of seeing all the BrBa/Better Call Saul parallels, too, as if every single time the director uses a similar frame that was used during Breaking Bad its somehow meant as a callback. It's not. Its called repetition. And even the writers' little nods and winks that intentionally call back to the other show are no longer needed. There's being self-referential, and then there's just being lazy.
The entire premise of Better Call Saul is about Jimmy's slippery slope to becoming the Saul Goodman we see in BrBa. The idea of a man trying to be good, trying to do right for his family (Chuck), is a well that the writers have gone to before with the result being one of the greatest television series of all time. Only Walter's descent had greater risks, greater highs and lows. Saul's story is the watered down version. He doesn't get cancer (although I think it's safe to assume something will happen to Chuck that sends Jimmy in a tailspin), he just can't escape the huckster side of himself that seems to want to part people with their money.
Like I said, it's a good show, but it will never reach the operatic heights of its original beast.