Making LP tradable seems like a good idea. I would simply put them on the normal market. But how do you do that? You buy certificates worth x amount of LP. So if you had 1,000 LP with brutor tribe you could buy a 1,000 LP certificate in the LP store. You still have 1,000 Brutor Tribe LP, but now you can sell it on the market.
An interesting thing about this method is that you can actually lose the LP if you get ganked while transporting them.