I actually like the idea of being able to hire nobles for tasks. I like the extra layer it adds to the economy. The mechanics might be somewhat tricky, but I think it could be reasonably.
New hires sign on at the end of the month to the noble offering the most gold per month.
TELL who command Give a command to a hireling FIRE who Release a hireling from service. Unpaid hirelings leave the service of their noble. Hireling may not be given orders directly. They may only be instructed with the TELL command. Hired units would probably keep their possessions separate from their employers.