That would just make him snowball again. I don't think giving any character the Bebop treatment is the right move.
Viktor only needs a small buff or tweak to spike back up, otherwise he will be Mundo. Giving him back 30% lifesteal plus a minor change would make him broken again. He's not the only characters being able to afk farm and take over, the investments should be spread out more evenly long term. IMO
Honestly, Dr. Mundo is exactly what I want to get out of Viktor — a slow but tanky character with regeneration. He was basically like that until they beat the hell out of him.