For anyone else who may come across this post… my solution, rather strategy is simple:
After researching the true security value of open_basedir configuration, I realized with ModSec, 3 different levels of application firewalls, and my entire site residing inside of debian 10 / ispconfig user jailkit, that it would probably be safe to deactivate the open_basedir option inside of ISPConfig on the individual site level by adding the word “none” in the field located at Domains >> Websites >> Options >> open_basedir.
Then to update fix all the file paths used by plugins in the multisite that still point to locations that you have migrated away from (make them all reflect local ISPConfig jailkit or whatever else location of the new wp-content folder)…once that is done reactive the open_basedir by removing “none” and saving the settings.