AppImages aren’t really ever technically installed so the process is easier than standard packages in my opinion.
However, the ability to give exceptions to trusted sources would depend on the distro to implement that and it would require someone to curate a list of trusted sources.
I think if there was a warning to tell them they need to grant the AppImage permissions that would be enough. It’s not difficult to do.
It’s not a requirement. Users can use the GUI method which does not require sudo at all.
AppImages don’t need sudo to run and they don’t even need to be installed at all. The only barrier to entry is the “make executable” situation that I feel is important for security and so easy that it shouldn’t really be a barrier especially if a user knows to do that.
We need to ask developers to include the how to make executable when they distribute their AppImages even if it is just a link to that thread I linked.
The more and more people who use AppImages then the more and more who will be accustomed to the make executable permission need and this issue becomes a moot point.