You tell him that him that if “you build it” you must be the medical director. So, he may need to alter his time table to accommodate your licensure. You are not some former lab supervisor who now goes around setting up in office labs for docs. You are a physician/pathologist.
If you let yourself be a door mat you will get stepped on.
And he can pay for your license and any travel to whatever state this is as well as your initial consulting fees and your director fee. If he does not want you as director for what you intend to charge, don’t do it.