I hope you understand it's incredibly unlikely your design will get approved by the copyright office, and if the LL team wanted to they could completely ignore you with no penalty.He pretty much made no contract at all. It was never even volunteer work in the first place. I was never a "volunteer" until the volunteer server was created, basically.
Never got paid, never commissioned and the fact they tried to claim it was a group effort because of colour suggestions is daft to me.
But that being said, they changed the design anyway and the project is crashing and burning, so it won't even matter down the line when it gets approved or rejected.
In all honesty he doesn't *need* a lawyer for this stuff. In the majority of cases, as long as there is a clear agreement inbetween the two parties, even something as simple as having them say "I give you the rights to use this", then there's not much they can do if they changed their mind later. For an even stronger case, he could just write up a form that says "I X hereby renounce all rights of character Y to Z for use in commercial and non commercial products now and forever" with a little dotted line at the bottom. And it would work just fine.
It's really not as complicated as most people think.
A judge would even accept a non-written verbal agreement as long as there's a witness to it.