Simple Way to Make Support More Attractive
Whenever I think about heading to the Rift as a support, the major drawback that keeps me disinterested is the fact that I need to use one of my six slots on a sightstone. Don't get me wrong, I think the support role should be doing this, but you feel incomplete as a champion. There are other reasons that the support role isn't very popular, but for me at least, the sightsone slot is the main culprit. My solution to this is if, and only if, you're given the support role, you should have the ability to upgrade your free ward to a sightstone at level 9. It should cost gold, but it shouldn't take away from your build.
Now you might say, wait, that's too OP having a sightsone slot AND six items. I don't think so because you are forgoing all farm, you're a lower level than most players due to less XP gains, you're sacrificing a lot already for your ADC to do work. And even if it does get to late game, and you have a full build and a sightstone, that should be a perk of the position. You did it, you got your team to late game by warding and supporting them. You deserve that and I think it would really bring a lot of people to the role since it would be the only one with this unique ability.