Although he might fit in as a peaceful mediator, the idea of him being the aspect of the mountain itself would be a bit strange, he would quite literally be the common ground they all shared. The others all represent heavenly bodies, where the mountain is very definately earthbound. It just seems like a really odd fit that they'd have to stretch to make work. Or they could stretch it all the way to Space Paladin Taric, who knows? (Please let this be a skin at some point!)
From a gameplay perspective, the idea of using Earth based magic to protect others might work, but it would really limit what could actually be done with him that would be cool, especially since a lot of it could easilly just end up being the same kind of raw passive power thats limiting him at the moment. Taking a more direct protective approach would lead to a lot of overlap with Braum and Tahm, where a tanky CC bot would do little to differentiate him from other CC heavy supports. If you focus more on his healing/shielding then he's going to clash with Janna, Soraka and perhaps Nami too.
Its one of the first skins I bought, simply because my WoW Paladin had that exact T5 set, complete with Hammer of the Naaru. I couldn't not own it.I am certainly okay with this. One of my favorite skins.