Given the $99 limitation has been lifted it seems reasonable to make general federated "App Store App" that downloads source and puts a build of an app on the phone, wrapped with a pretty UI and clever control channel to your "dev" machine. Value of a particular "store" would be in its own curation. Seems Apple developer portal has enough API to get provisioning keys for Fastlane, might have more generally interesting stuff to make other features like APNS seamless.