Thanks all.
CCdaCE, I talked about it with my boss at company A. He's going to let me get settled at company B, and then we'll see what works best.
Meadbh, I still will own the stock and associated warrants in A. Those securities will either be worthless (if the company fails), or will be purchased from me (and the other ~150 shareholders) if the company grows and votes to sell itself a few years down the road. In the meantime, they are completely illiquid because A is not a market-traded company.
2Cor521