Problem: Frequent and even automatic live and installable ISOs are known to be good for testing and event just making sure nothing breaks. They should at minimum be part of any tinderbox style testing, and preferably mirrored for easy global access. However, ISOs are not rsyncable and require massive amounts of bandwidth to be sent over frequently to the many mirrors.
Preexisting bits: We have all the requisite packages already being sent to all the complete mirrors on a regular basis. We also have jigdo, which can compose media from a mirror or a local data store.
Solution: Create either a push command from the mirror manager, or a pull command available to the mirrors to let them know good media can be composed from the current existing up to date bits. After a mirror updates itself, it can then use an automated script to generate media using the preexisting media compose tools we have and jigdo if needed. The md5sums can be used to verify that the media composed locally is the same as the media composed by our tinderbox testing system.
Pie In The Sky: In a local infrastructure where one mirror box pulls from the central mirror, and then the local boxes mirror the local source, the local mirrors can be configured to just pull an ISO from a local source. Likewise, a compose box could be set up to do the composing separate from the mirror, which could also make the ISOs available.
Well, it's just an idea. If only there were another 8 hours to the day.