Would it be possible that for a week once a month, in a rotation with each other, the old Adventures were brought back to the sandbox as “Retellings”? No Man’s Sky has a similar mechanic called “Expedition Reduxes”, which is basically an old narrative event on a separate fresh save replayed during update downtime.
All the old titles could possibly remain locked as a proof of experience (I don’t see why people can’t earn them but I already know a lot of veterans would be upset their titles are more common), the idea is just that the old content is brought back to the sandbox for players that didn’t get a chance to experience it the first time.
