He'd mostly likely just pull a Trump and bathe in the controversy.
One thing that is certain about Shadman is that he loved the controversy because it gave him attention, he loved being in the spotlight (this was true then and it's most likely true now).
I'm sure by now we are aware of the infamous artwork that he made of Keemstar's daughter but that is what made Shadman to be Shadman, he is a guy built on controversy and he knows this.
If tomorrow Shadman came back, the Youtube commentary channels would talk about him for months on end and Twitter would explode over this because he knows that he's still relevant and he can get rich by capitalizing on his own controversy.
If Shadman comes back tomorrow, he'd probably just do what he's always done by being the center of attention for him to stay relevant; the longer the Internet keeps talking about him the stronger he gets unfortunately.