Photographer Pay Per Hour

Having a way to do photographer pay by hour instead of by service would be super helpful. (Paying according to estimated time on site duration) Perhaps for the admin they can go into each photographer and add their pay per hour amount (in case some photographers get paid more). The invoices would calculate how much estimated time was spent on site for the photographer at the end of the week and times that by the pay per hour price to produce the weeks total price of payout.