I have my own idea; why not extend the play off positions to include the bottom team from division 3? This way, instead of getting relegated they could, by playing every team above them, and winning all their games, be promoted to the Premier League!
However, should they lose any one of the games they should be demoted to the Ryman League, Division 1 South.
This should enable the play-offs to go on for so long that they won't finish until mid-way through the next season, by which time the teams involved in the play offs will be so far behind everyone else they'll probably need to go through the play-off system again.
This way by season 2025/2026 teams involved in the play-offs will still be in season 2014/2015. Sounds ridiculous I know, but the main thing is to keep the season alive for more clubs for longer.