Installing an app by clicking or picking it up from a menu seems natural to me.
This is the way things are done on almost every OS and the appmanager has plenty annoying popups about safety.

If we're to be concerned about safety, then let's make the easy installation of .debs possible with a commandline or a mini-app like rootsh.
But having more installation files and having to "dpkg" them all really makes no sense to me.