Why not reviving Heimerdinger as Support?
Speaking both as a support main, and given that Riot is looking at putting more supports in rotation (which probably means more bans of supports in lower tiers), I found myself thinking about good ol' Heimerdinger:

He is a support secondarily -- according to the current Riot interface. He has a passive heal - which is a bonus for the adc. He can place a turret in the bushes in the river to make warding by the other side and/or camping by a jungler/ganker harder. (Remember that those turrets activate when a stealther is nearby - added bonus.) Plus he could set up a small "safe zone" for the adc to fall back to. As an added bonus, when the adc is horrible, Heimer has the potential to carry or help the team catch up at least. Is it time to bring him back into consideration as a support champion?