Sometimes there can be an issue that certain repos can't be accessed from certain countries over IPv6. This is for example a current issue with Fedora: https://discussion.fedoraproject.org/t/f42-error-503-when-trying-to-update I don't know if something like this could be implemented with packagekit. But it would be very helpful to have a setting to force IPv4 in such cases and not have to use the command line for it.
This isn't a setting that makes sense to have in a specific app. It could perhaps be systemwide, but that already exists. :)