Is this a small opera company that you are helping on the cheap? Because what you really need is an Asset Management application for Theatres. Preferably a web- or cloud-based one that any authorised person could access. A quick Google will find some, such as what looks like a web-based and iOS (perhaps Android as well) Device based solution like that provided by
Theatre Safe Australia. (I just Googled them. I don't have any affiliation.)
I've had a think about it, trying to work through the issues with using MC and making it available to everyone. It isn't worth it. It would be a bodge, and not a good one, for several reasons. Everyone would have to have a copy of MC on a PC they can access where they need to use the "database". Licences. Hardware. etc. While the images could be stored on Google Drive, you would need an App to allow Google Drive to appear as a drive letter in a PC, for updates to tags in the image files, or in the MC Library. There would be no file sharing capability on those files on Google Drive. Updates could clash. Each user would have to act as a Client to the MC Server. You would need a MC Server that was always available, not a laptop. The Server Library would have to be on that server. Hence, the image files might as well be. No need for Google Drive.
The above is just a bit of a brain dump, without knowing the actual requirements.
Maybe there is an App that can work with Google Photos to make tagging easy. But I agree, Google Photos isn't easy to use for tagging or viewing tags. In fact, it is very basic.
No, you really do need is an Asset Management application. Preferably one that suits Theatres. I know, it is probably overkilled for what you need. Hence my first question above. But there is bound to be something out there that is web-based and has Android and iOS Apps for mobile use on site.
i.e.
https://www.segbaysoftware.com/ Cloud version would be best. Not free.
This is old, but some ideas here:
https://www.quora.com/Can-anyone-reccomend-a-simple-Saas-Cloud-based-Fixed-Asset-tracking-software-that-is-not-IT-focused The good news is, what you have built in MC with tagging would be a great resource for setting up an Asset Management system.