Let me get to the point.
You can't save test cricket by limiting the number of T20 games played. Instead, inject aspects of test cricket in T20.
For every 3 T20 games, schedule 2 T20 games that have elements of test cricket. Let us call them a Pace20 or P20 and Spin20 or S20 games.
In Pace20 (P20) games, the pitch is that of a first day, first session test match pitch with bounce and swing. There are no restrictions on how many overs a bowler may bowl. The team with the highest average score wins (not the highest score) - tried as an experiment to see which is preferred by audiences. The game is for 20 overs. Play this game with the red ball. There are no fielding restrictions.
In Spin20 (S20) games, the pitch is that of a fifth day, third session test match pitch with lots of turn. The ball is one that has already been used in a prior T20 game. There are no restrictions on how many overs a bowler may bowl. The team with the highest average score wins (not the highest score) - tried as an experiment to see which is preferred by audiences. The game is for 20 overs. There are no fielding restrictions.
Schedulers can figure out how you have the right proportion of P20, T20 and S20 games in a tournament. Each team should play the same number or P20, T20 and S20 tournaments. The finals of a tournament should be best of 5 games with a P20, followed by 3 T20 and an S20 game.
The thought process:
P20 and S20 games will give you all the skills that are important to cricket, and limit the duration of the game. It will have aspects of endurance as losing a wicket is lot more significant than a T20 game. Roster selection and strategy in a tournament becomes very interesting.
