Accounts should have a theme: a color scheme, a background image, notification sounds, a whole unique look-and-feel.
Please don’t laugh, I’m not proposing this because it’s cute (though it sure is); it is for security.
When I get home, I feel home: the things around me are familiar, I know I’m in a SAFE environment (and if something is out of place, I would spot it without any conscious effort; it’s automatic). Similarly, my Chrome accounts are themed differently: I immediately know if it’s my “work browser” or my “play browser” just by looking at what color my tabs are, or the puppy or the kitty in the corner. Qubes OS uses a similar concept to visually differentiate between the “security domain” (implemented as a VM) that a window belongs to:
The implementation is super simple. Themes are just data, stored in the cloud as everything else. When I log on with my account, the launcher downloads the theme referenced by it, and it makes it available to the apps. If an app shows up with the proper theme, I can be sure that it went through the launcher, and it’s not just a look-alike.
Also, it will help differentiate between my multiple identities, when the launcher supports logging on to more than one at the same time (as it should.)