Elemental Dragon Buff Idea!

I was reading up on Riot Meddler's post and noticed you guys had mentioned possibly introducing a "new elemental dragon buff". In regards to "not wanting to make tankiness a problem" or "making people hard to respond to", what if you did a DEFENSIVE BUFF that wasn't directly linked to champions? What if it was something related to the map? Or strategy? Something that could be fun to play around (and potentially even be a little bit of counter play for the new tower smashing Rift Herald??)

TL;DR What if you made a "Reverse Mountain Drake" type of buff? Where towers were harder to take down for the enemy team???

You could do something like what has been done in Nexus Siege, where if a tower hasn't taken damage in 'x' amount of time, a small shield will be applied to it? Like a mini-Janna shield but longer-lasting? And each elemental dragon of that type could increase the shield size?

The shields wouldn't be too huge, since that'd be OP. But large enough to make a difference. Just a thought! Hopefully this gets worked in. I feel as though it would be fun to contest over and relatively easy to balance. I understand that more recently Riot wants to speed up games...but I do think this would be a really interesting buff to play around. Thanks!