Tank/support concept

I've always thought the idea of a tank/support who can't generate mana naturally, but instead either gains mana from taking damage or by stealing it from enemies would be kind of interesting... Though I do realize the power behind someone being able to steal mana. Then make it so rather than having any offensive abilities, all of their abilities are pure support, maybe similarly to Taric but with literally zero damage scaling anywhere on his kit. Someone who, like Braum and Taric, is a dedicated front liner, keeping the rest of the team safe and keeping the enemies in their place. I don't have a whole lot of ideas on an actual champion along these lines but seeing one would be interesting... if a bit difficult to make possible gameplay-wise. I feel like it'd be something along the lines of Mordekaiser, where he's either really good or complete trash based on whether or not he can get his shit charged or not.

I feel like for this kind of thing though, mana regen would have to have special scaling for him that increases the mana he generates when he steals/is damaged (depending on where it ends up going) and I feel like he'd need a taunt passive in the style of Gangplank, where he can only taunt every so often, or like Nautilus where he can only taunt each individual target every so often, assuming it goes the route of 'take damage gain mana,' since he'd basically be like old Taric... He'd be there, but he wouldn't really be doing anything unless someone decided to go bronze and focus him.