I just encountered a situation where I wanted to transfer a license and sheets at the same time, and was unable to do so without a workaround. I had to either get the person to transfer all their sheets to me, then change the license, and switch them back to the new owner, or take a license away from another user, give it to the new user, transfer the sheets, then the license back to the owner I took it away from.
This is a painful process, and gives opportunities for items to be lost. Realistically this should be an option in the dropdown when changing licenses.
I have already submitted an enhancement request in the form.