To get an epetition started it needs to meet the criteria described here: How petitions work (parliament.uk)
In short it has to be for a specific action, and there can’t be any other current ones petitioning for the same.
What the epetitions for rejoin have all had in common so far is that they are written by remainers for remainers. It may be interesting to start a petition that is written in ‘brexlish’, asking for a closer relationship with the EU but using language that will appeal to the ‘not the brexit I voted for’ brexiteers. For example, an epetition to restore FoM could go under the cover of “freedom of residency for Brits to retire where they want in our continent”, and give Torremolinos as an example in the text.