Of course, it is easy. When you're already assuming something like RSS feeds for app updates exists, don't you think it's possible to have an application download them once a week and update all apps automatically? For an end-user, there's no difference to APT.
Also, you seem to misunderstand the point. To have a third kind of distribution -- "stable foundation and recent apps" -- doesn't affect your choice of distribution, at all. When you're satisfied with Gentoo, you simply continue using it.
> When you're already assuming something like RSS feeds for app updates exists, don't you think it's possible to have an application download them once a week and update all apps automatically?
So where can I get this program you speak of? Why doesn't it exist? (edit: and if it doesn't exist because you don't even have RSS feeds, isn't it even harder than watching those and manually installing?)
Check Sparkle [1] as well as AppFresh [2] for MacOS. The former is even available under the MIT/X license. No need for central repositories when done right.
Also, you seem to misunderstand the point. To have a third kind of distribution -- "stable foundation and recent apps" -- doesn't affect your choice of distribution, at all. When you're satisfied with Gentoo, you simply continue using it.