Majority of the members here are out of N. America and we don’t have the power sliding door option. That said, it sounds there this can be an easy fix to use one trigger to activate both doors.
It sounds like there are two independent switches on the dash for each door, correct? Take out both switches, are they the same and do they have the same number of leading wires in the back? If you take out the driver side button, can you still activate the driver side PSL with the remote?
IF both switches are the same and the driver PSL switch has an extra wire, it may be an easy fix but that’s a big IF. The BCM simply sends a single to the driver side door relay, which in turn powers the motor to drive door. If you can identify this wire, there is a high probability that you can tap into the other door's switch or relay and control both at the same time.