I know it's a longshot, but since I don't know how to do anything with meshes myself I thought I'd just put the idea out there in case some other modder is interested.
When I hear the word 'Briar' I'm thinking thorny brambles and can't help but feel a little disappointed that the forsworn Briarhearts don't look even a bit briar-y. I think it would be awesome if the Briarheart body-armor mesh wasn't a fur skirt with a hole in the chest, but like... brambles growing out of his skin and wrapping round the limbs. Like it's a melding of plant and human, similar to how the hagravens are part bird part human.
I haven't found a whole lot of official lore on the actual forsworn beliefs or even what kind of plant these briarhearts come from, although there is something in ESO about a tree they grow on I think? But it seems like they ought to come from a vine given the name. So it might not really be "lore friendly" but I think it would look cool.