Depending on just how large your employee is they might not be able to sit in the exit row; the flight attendants might move them to another set of 2 seats for safety reasons. I know that might sound harsh, but someone that large might have a hard time performing the duties at the exit if something were to happen.
Every year in recurrent training the f/a's are required to pass through a window exit to determine speed and ability. If you can't get through it in a specified amount of time, or with a certain degree of ease then you are taken off the line. Same pertains to a passenger seated there, if the f/a's don't feel they could open the exit and egress through it quickly then they will probably reseat them.