I reckon they should have a round-robin of matches against each other:
3rd (at home) Vs 4th
3rd (at home) Vs 5th
3rd (at home) Vs 6th
4th (at home) Vs 5th
4th (at home) Vs 6th
5th (at home) Vs 6th
and, forget win/lose, the team who have the better goal average over the 3 games goes up. Sounds fair to me (the better finishing clubs have home advantage) and the money grabbers at Wembley don't make a bean.
Best one, as I put on here a while back, is:
5th play 6th (one leg)
4th then plays winner of the 6th v 5th game
3rd plays winner of above game in the final
Therefore 6th and 5th teams have to win 3 matches to gain promotion. Team finishing 4th has to win 2 games to gain promotion and 3rd place has to win just the 1 match.
At the moment there can be little incentive as to whether you finish 3rd, or 4th, or 5th, or 6th and it can quite often just come down to which team is the form team of the moment .
With this system it would promote the need to finish 3rd and then in turn 4th and then obviously, 5th. Each team would be rewarded accordingly.