The inability to have more than one policy installation running at the same time is probably a bit of a holdover from the R77.30 and earlier SMS. In R80+ management, when a policy install is started the needed config data is dumped out of the postgres database back into files like objects_5_0.C, then the policy verification, symbol resolution, and compilation into INSPECT code proceeds more or less like it did in R77.30 (with some new optimizations). I'm assuming that this "dumping" behavior is for the benefit of legacy SMS processes like fwm that are still actively involved in many management operations. Until those legacy components go away (such as the HTTPS Inspection/MAB config still being in the old SmartDashboard via fwm), I just don't see how more than one policy installation can be running at a time on an SMS.
The ability to queue policy install operations should be possible, but what about an administrator that queues three policy installs, then immediately makes some changes in a session and hasn't published/discarded yet, should the queued ones still be allowed to proceed? What happens if multiple policy loads are queued then that same administrator makes changes and publishes them before the queued installations are all done? I can see some rather confusing situations that could arise here. An administrator with queued policy installations would almost have to stay locked in read-only mode until they are all done, but then what if some other administrator publishes new changes in the meantime...ugh
Gateway Performance Optimization R81.20 Course
now available at maxpowerfirewalls.com