I don't understand your question. You can sell/assign membership interest in an LLC (although a member of an LLC can't take W2 wages from it). You can even call it stock.

The problem with this arrangement isn't going to be legal formalities. The problem's going to be that your tiny minority investment in a private LLC is going to have no protections against dilution or unfavorable buyout. It's possible that the only recourse you'll have if something goes wrong is to be such a pain in the ass that they'll buy you out.

Note well that you will not be able to sell or transfer your equity interest in the LLC to anybody else.