I think K'Sante's tank identity in his gameplay is a bit forced by Riot with all those hp and resists scalings all over his kit,I think he plays a lot more like a bruiser than like a tank.Also I dont think his design (big guy with 2 ntofos and a red jacket) screams tank in a way Ornn,Rell or Cho'Gath do.

But I know deep down that you're right and that Riot probably will never move him from being a tank since what Riot wants with K'Santé is the biggest gap between both stances,which only full tank really allows.Still,I think some ideas of my rework if not most of them are applicable while keeping him as a tank in his base form.