Thank you for the suggestions Chris, appreciate you taking the time.
Yes I also work like this, ie creating dummy accounts whenever required and replicating the user's access rights and memberships etc. However this can get very complex when they have multiple memberships and/or expiry dates. Joomla access levels can easily be replicated, but replicating everything including membership history etc (for example to test configs eg whether the member is offered the appropriate upgrades or other plans depending on their status) becomes very complex.
Nothing would beat being able to instantly login as that person and being able to see what they see immediately rather than trying to replicate their exact history and situation. This should be an access right of a Super Administrator in my opinion. At this point we have to imagine what users are seeing based on the config settings we set, difficult to confirm the config is working as intended for all membership situations. A simple login as various members would be instant confirmation of settings, and also would be invaluable for troubleshooting if someone calls with an issue... I hope that make sense?