I guess we might need to put a bit more thought into this again.
In real life, there are two ways to operate a bus stop.
a) the stop has a schedule
In that case, passengers to various locations wait up there for their correct bus, which will arrive at a given point and then leave shortly after that. Buses with no assigned jobs or out of schedule wait at a dedicated parking lot often part of the bus station. The bus stop will be empty of vehicles most of the time as they are there for only a small time window.
b) the bus waits for PAX and leaves when full
This is more like the overland stops. A bus waits for passengers to arrive and leaves the stand, when its job is done. This requires 1 stop per bus as it occupies the stop for a long time. This is, how it is implemented currently, I think.
So, if we want it to be more like a) and we are able to use more buses on a stop, the buses must operate like e.g. check-in desks. PAX will wait there after boarding remote and at a certain time they will be collected for their flight. Arriving PAX are simply unloaded and then the bus leaves again to free up the stop. In the meantime, the buses will wait at a service car stop or dedicated bus station - this might be a nice thing to have as we can sort out what parks where and what looks good.