Mana Tree--The new Support
Shoot--I don't know how to add an image here. Anyway, know how we have a few supports who heal? What about mana? Did we forget mana?
Think about it--a giant, immobile spiritual tree...takes a long time for it to be rooted from one area to another. Or--like Skarner's crystals, give it an ability to teleport from one growing site to the other all over the map (ie a spot in each lane, a spot by dragon pit and baron.)
Why all the trouble for mana?
Well, it's not just a mana tree. It also has glorious abilities. For example, it has an ability that releases fairies to fly around the map dealing AP damage to enemies. It has an ability to grant shields to allies on the map, and it's ultimate can be a wave of energy through the map that can shield all allies from all harm for .5 seconds (I think that's half the duration or Kayle's ult, but global?)
If you don't like those ideas, then you can make the tree have a gnome to control, bunnies, the fairies again, and other shields/buffs/etc. The possibilities are endless! It would be a SOLID force for a team and almost unkillable, but again, immobile and mostly based on ally mana regen.