Consider restriction time as capture time in Scheduler
When using the Scheduler, the StartAt constraint specifies at what time a particular observation should start.
Currently, that time is the moment the Scheduler starts processing the job, and proceeds with Track, Focus, Align and Guide steps, as ticked for the observation. Then Scheduler triggers Capture, incurring a delay sometimes as high as a few minutes.
However, the StartAt constraint specifies at what time the actual observation, that is, capture, takes place. In order to comply with that restriction, all preliminary steps should be completed before that moment. Scheduler would start processing steps in advance, and remain idle or guiding until the required time.
The StartAtCulmination constraints and StartAt timestamps calculated from StartAsSoonAsPossible constraints by the Scheduler when sequencing observations probably do not need such precision.
Because it is difficult to foresee how long preliminary steps may take, it may be useful to define a manual lead time for the specific purpose of preparing the constrained observation. Recorded statistics on the duration of each steps may be useful for that purpose too.
Capturing satellite transits in front of or star/planet occultations with the Moon may be a good validation test.