Packages managed by Gnome Software (Ubuntu 16.04)

Hello everybody,

I have several questions about Gnome Software on Ubuntu 16.04 :
1. Why some packages are not managed ? For example, I can't install weechat via Gnome Software,
2. How I can install my own packages from my own repositories via Gnome Software (like I do via Ubuntu Software Center) ?
3. How update Gnome Software cache, yesterday I have installed Ubuntu 16.04, and Gnome Software returned no result when I searched a package. Today searching returns results, so I think there is a anacrontab/command/script to update the cache.
4. Gnome Software will replace Ubuntu Software Center ? If yes, Ubuntu Software Center will not be maintained ?

For my needs, Gnome Software is not a good alternative to Ubuntu Software Center because we can't install/remove any packages from any repositories, like I do with Ubuntu Software Center with my standard users via policykit rules (Synaptic is not a alternative to Ubuntu Software Center because this is a tool for administrators which also allows to configure repositories ...).

Thanks for you answers and have a good day ;)