We can easily repoint rockpool to any other appstore, even to spin off our own. The problem of course is development lifecycle. Also our group is tiny part of the whole pebble community, so better to look at the direction of the mainstream.
Only if they will be totally helpless - as last resort I may write simple crawler and pull all apps from apstore making some stub replacement.
Anyway it's not for a long, new HW is not produced, so as soon as all hw pieces die - there will be no need in such stub/replacement.