Adding block trim

Hi,

I'm actually working on a small mod for a couple of friends that would add 'Block Trim', basically just a small thing that we would be able to add at the edge of the block (like the image below).

My question is : Is there a way to make it so each side of a block has four different positions possible. My guess is that I would need a way to detect where the player is looking on the face, either with something like an area on the UV map or the closest edge. 

Thanks a lot for your help,

Bismuth_Bi

P.S. Eventually I'll like to be able to add more than one trim on the same face, but one step a time.