I think SGA is too good of a scorer overall. I just can't imagine Steph averaging close to 30 ppg.
I understand what you mean, but i think SGA is his trajectory. Shea was a better shooter at this point, but Steph is a better playmaker than year 1 Shea.
You have to take into account circumstances too. If SGA played for Detroit and not in a pure 5 out system, he wouldn't be scoring 30 either. If he played with another ball dominant player, things would be different as well. A lot of things had to come together for Shea to become what this years Shea has become. I think, if given a system and circumstances like those, and an improvement in his shot over his first few seasons (this always takes a while), he could be that type of player.
I sincerely doubt that all those things come together exactly the way they did for Shea, but if by some miracle they did, then i think that's his comp. If he's a similar player in a terrible circumstance with no spacing, then maybe his ceiling is a player like this seasons Cade Cunningham. I think these 2 players have some real similarities in their games. 1 of them is in the best possible situation, and the other is in maybe the worst.