The only way I could see this work is the following:
Aidan kills Diablo. Aidan is consoled by Adria and eventually conceives Leah with her. Aidan realizes Diablo is overcoming him and makes plans to set off to the east to get it taken care of. With the last trace of Aidan's humanity, he realizes it's a losing battle to contain Diablo and he'll soon end up like Albrecht, and without thinking rips the soulstone from his head and jams it into the forehead of another man who quickly becomes the Dark Wanderer. Aidan then sets off into seclusion, driven to insanity. Aidan comes back after 20 years, after working off the insanity, to help find and defeat Adria, the woman who turned his daughter into a manifestation of the prime evils and eventually to her death.
The only issue with this is the D2 cinematic where Marius is following the Dark Wanderer and he mentions that he learned about him and how he used to be a great warrior, obviously, leading us to presume he's talking about the hero who beat Diablo below Tristram (Aidan). But maybe Aidan put the soulstone into a fellow warrior. I haven't thought that far yet. I'm sure Blizzard would be able to make lore around this guy that could fit pretty well.
Anyway, like, dislike, love, hate, got better ideas, "dude give up and stop trying," other issues or contradictions to the lore- what do you all think?