It would be very productive to be able to use the Processing Area tool prior to running Step 1 to split a large project into sub-projects.
This way the user can control the overlap and the inclusion of existing GCP’s in the overlap so that the creation of MTP’s can be negated or lessened.
It should be a simple matter of ensuring that cameras shown on the map screen that are not within the processing area are disabled (using the cameras lat/long?) and then the project is saved as a sub after disabling the cameras is complete. once that sub is saved, all cameras would be re-enabled so the next area can be chosen. This would allow for multiple subs. It would be helpful if some annotation indicated how many cameras were being left enabled.
Since only one processing area is allowed at a time, then some sort of box representing a previously created sub would remain so that proper overlap can ensured.
Currently the only way to do this is to pick cameras in map view (remember, this is before running step 1, so as to avoid processing all cameras), note the lat/long, and then go to the camera tool and sort by lat or long and disable those with lat/longs greater and less than cameras chosen as needed, and then saving as a sub.