Hm, good question. I think he would have wanted to go into teaching. Perhaps a tenure as a professor for history? Or maybe he would have gone into something to do with plants.

Although, firstly I think he would have traveled the world before deciding what to do with his life.

I think personality wise he would be less closed off… lighter in a way that’s real instead of the faked light and softness he carries himself with. He’d be more the person he is in private with his trusted loved ones in canon than all the masks he wears like impenetrable armour. I also believe he would not have has harsh opinions of the world or be as cold blooded as he is in canon. He’d certainly be a lot less traumatized too. Also, I don’t think he would have met his wife and had Sophia if his life had been in his control, which is interesting since fatherhood was an impactful and positive experience for Ivan in canon.