How about something like this?
Distro author: A consortium or company or individual who wants to do the work to maintain and check versions and create example sites etc. Same way as plugins work now. Just its like a meta-plugin.
Plone: Includes something like https://github.com/collective/plone.cpanel. Which provides the inferstructure built into plone for multisite and to let users create sites with a prebuilt profile or content nicely. e.g. one click blog site, one click uni department website. This also means users get the same experience no matter which distro they choose.
Plone.org and installer team: Provides the installers and links to cloud providers that not just vanillia plone but a subset (or all) plone distros can be installed easily. So instead of having a docker image for just plone 5, having plone5 or eduplone, or plonegov for local gov, or plone intranet. This lowers the barrier for the distro author so they can concentrate on the content rather than the installation.
Hosting providers: They want good apps to install. By giving them not just plone, but ploneedu etc, they are happier. They have something better to offer their users that makes their platform more attractive.