Unintuitive user interface when adding new users and multiple user templates/parents are available

[teppokoivula]

Not entirely sure if this is an issue or a feature request, but either way:

If I enable multiple templates/parents for users ($config->usersPageIDs and $config->userTemplateIDs) and go to Admin > Users to add a new user, I have to choose both parent and template. The problem is that since my custom user template can only be used under a specific parent page, it's pretty easy to accidentally pick /processwire/access/users/ as the parent for said custom template, in which case the result is somewhat blunt The template 'MyCustomUser' does not allow parents of type 'admin' error.

That's understandable enough for me, but this does not feel intuitive enough for a non-technical client. Is there any way that these two fields could be dependent so that one can't (easily) make a "wrong choice"?

I figured I'd solve this by preventing adding any custom users from Admin > Users (via injected JavaScript); it's a bit hacky, but would likely make more sense for the client. The problem with that approach is that, as mentioned in #1278 , currently it seems to be impossible to add users with custom templates directly from page tree, even under public pages.