The new package format called AppImage is just awesome and integrating it on the sistem will bring it closer to what Microsoft Windows has to offer!
In the current release (15.4.1), even if i make the .appimage file executable through properties, i cant open it with double left click, i can only open it through terminal.
My suggestion is to implement the AppImage Daemon on the system and make, by default, every .appimage app executable. This way we will have a gorgeous App Store and also a really easy way to install apps through the browser!

Thanks for your attention!