FWIW, I'd go with:
16 team Premiership split into 2 leagues of 8 with promotion and relegation 2 up, 2 down via playoffs (playoffs not universally popular I know, but commercially necessary in reality). To get an idea of how this might look, based on last year's final tables, Premiership 2 would still include Wasps, Bristol, Newcastle, Worcester and Bath, plus Ealing, Doncaster and Cornish Pirates from the current Championship to make things a bit more interesting, so still plenty of eye-catching fixtures there.
European competitions to revert to pools of 4, giving all another guaranteed 3 home games.
New English national knockout cup involving all 4 tiers of the National Leagues (currently 81 teams, rising to 82 next season if all goes to plan), preliminary round between Nat 2 teams to take it to 64 ahead of straight knockout from round 1 involving Prem, Champ and Nat 1, with early rounds played during international breaks and Prem teams fielding development sides similar to current Prem Cup, but later rounds (Q Final onwards?) to be scheduled to allow top teams to field a full strength team and hopefully generate more interest (and £££) from sponsors/TV/spectators giving a financial boost to clubs lower down the ladder as well.
That's a guaranteed 10 home games a season, plus likely some knockout rugby here and there.
If it helped raise interest across all clubs then I wouldn't be averse to having centrally contracted England players spread more equitably around all the 16 Prem teams via some sort of US style draft (not sure exactly how these things work as I'm not really a follower of US sports, but I know some on here will have a good grasp of it). I know this is sacrilege to some, but it would take some of the financial burden off of the clubs, should mean that all clubs have at least 1 or 2 England players to draw in the crowds and would put a stop to certain clubs hoovering up all the emerging talent from other clubs whose owners don't have such deep pockets.
Something radical is needed as it is increasingly clear that the current model just ain't working.