We are in a similar situation. I have multifamily, commercial and single family and staffing everything correctly can be a nightmare, especially mixed with the logistics of windshield time and the many different request and expectations that vary be each owner.
For me when I have a 200 unit building, it is ideal. I can build a staff and have the property pay this alone with management fees. The smaller portfolios and single family properties get tricky when you have a few hundred, collect a management fee, but do not have a good way to pay staff outside of maintenance (that is easy since they are paid when they are deployed like a contractor). I recently decided to take an upfront hit to hire a core team that will cost myself personally over 140K a year.... my option is to be understaffed, see service degrade and make an extra 100K until things fall apart. Keep in mind I am choosing a centralized system and have the goal of slowly moving away from the day to day operation of the business and focusing on growth, system improvements and ideally enjoying my life a little more :-). I want to create the customer experience and an someone dedicated 100% to owners as well as residents. I find lack or no response is one of the leading complaints across the board for all management companies that I hear on both small and large portfolios.
My quick two cents on your scenario. Add the following:
Leasing Fee on SF - it is typically expected
On multifamily use percentages for fees if you are adding value. I have raised incomes over 40%....if I had a flat fee I would missed out on the growth of the rents...plus it is an obvious incentive for the PM as well.
Personally I don't dig much deeper than that into fees since I see owners eyes start to gloss over. The simpler you can make it for owners the faster you can implement growth that is sustainable.