Thanks for the answer. My goal was to make the intended use clear. When I developed, I did better with hearing how someone would work with a new feature than just hearing a feature request without that context.
fwiw, and not speaking for others, but in my use, we could handle some pretty severe limitations, if that made development easier. The ol' 80% of utility comes from 20% of the work. For example, psw on an album would work fine, as opposed to having a one-many or many-many on users-albums. For uploads, there'd need to be a way to pick the album before the upload took effect so that orphaned pix didn't persist somewhere. Or a one-to-one on users to albums, i.e., when a user is defined, one attribute (characteristic? always confuse them) is the single album to which they can upload. Makes the upload processing simpler, be/c it can only go one place. Wouldn't need batch upload, either.
btw, this is just me thinking out loud...not being pushy or anything...
summarizing, a field in the user db that would hold the number of the allowed album, and another field in usermgr.php that would be a popup of all albums, and then an upload that's limited to that one album (I don't allow private/user galleries).........that's my 80% solution for as little development effort as I can think of today.
Thanks for humoring me.