My 2 favourite picks:
Rammus, the glorious Armordillo. They introduced so much stuff in the last time they could use for his rework.
Ornn and the demigods are the perfect base for his new lore, making him a Shuriman demigod of the earth. Camille's passive is the only example of an AD-shield in the game, which would work perfectly with his anti-AD tank thematic. They experimented more with speed scaling (Warwick out range, runes) and it would be perfect for his Q.
Dr. Mundo, the mad man of Zaun. I would like to go back to his "Dr. Jekyll and Mr. Hyde" thematic from the past. And ever since Evelynn got her update, I think he should be related to her. They kinda share the same skin colour and Evelynn regenerates health in demon shroud.
We know that Zaunites experiment with magic in a scientific way. I think it would be great if Dr. Mundo encountered Evelynn and is one of the very few who survived it. But he is a masochist, unlike Vayne who felt pain, despair and hate when she met Evelynn, he felt happy.
Maybe he got some kind of sample from Evelynn back then and now experimented with that demonic substance to create his highly durable body... to become the perfect plaything for his lovely goddess Evelynn.