Patrick,
Here are a few considerations:

1. Apartments for working people will have low loads during the day and high loads at night. The offices will have the reverse pattern. Depending on the actual office schedules, the actual residential occupancy pattern and the ratio of office / residential space, 50% might work very well. 50% may also be rather close to "irresponsible" unless the local population is very tolerant of room temperatures that are a few degrees higher than normal!

2. Regardless of #1 above, a LEED project should model the building based on the architect and Engineer's "Basis of Design" (BOD) document. The scheduling and diversity patterns I mention in #1 are not commonly part of a BOD document, but in your case they sound critical. You should (strongly) request this information! If you make assumptions that differ from the Engineer's you may spend endless hours trying to reduce unmet cooling load hours (and probably will not get paid for them)

3. Once you are confident of the schedules that have been assumed by the BOD, you should be able to represent them for the energy model.

Note: Because each apartment has two fan coils, each with a thermostat, you really have two zones. This may become important for the cooling diversity.

James V Dirkes II, PE, BEMP, LEED AP