dont bury it in the concrete.I saw all that. However, that doesn't answer my question at all.
But it doesn't really matter, because by the end of my post I had decided to have both circuits in the island. Likely split it in half, so that hopefully nothing gets overloaded.
Put in a jbox, and cap it off. But if you're gonna go to all that effort you might as well just put a receptacle on it like you figured.