The rules are not the problem the mechanics are, specifically the allowing of players to pick their own opponents...that above all else needs to change. I think almost everyone would be happy (except those who's only interest in the tournament is selling wins) if had three tiers of the tournament, 1 star, 2 star and 3 star decks and make the 'game' select player opponents based on which tier they are taking part in and not let the players pick their own.
Most important thing is remove option of players choosing their own opponents.
Here is what I would do...first and foremost remove the ability for players to choose their own opponents. That is the only way to stop the win buying going on which should not be happening in any tournaments, whether you do that through a roulette system or whatever I don't care as long as you remove the option for players to pick their own opponents.
I would make the tiers something like this...
Tier 1 (The 60+ card category)
First prize for top 3 is the legendary/collector cards + 150,000MGP, second prize for top 4-10 being 10 gold card packs + 100,000MGP, third prize for top 11-20 being 10 silver card packs + 50,000MGP followed by fourth prize for ranked 21-50 which is 10 bronze pack cards + 10,000MGP, the rest get 1000MGP perhaps for taking part provided play all 15 matches in a tournament.
Tier 2 (The 30 to 59 card category)
First prize for top 3 is 100,000MGP, second prize for top 4-10 being 10 gold card packs + 50,000MGP, third prize for top 11-20 being 10 silver card packs + 25,000MGP followed by fourth prize for ranked 21-50 which is 10 bronze pack cards + 5,000MGP, the rest get 1000MGP perhaps for taking part provided play all 15 matches in a tournament.
Tier 3 (The 1 to 29 card category)
First prize for top 3 is 50,000MGP, second prize for top 4-10 being 10 gold card packs + 25,000MGP, third prize for top 11-20 being 10 silver card packs + 15,000MGP followed by fourth prize for ranked 21-50 which is 10 bronze pack cards + 3,000MGP, the rest get 1000MGP perhaps for taking part provided play all 15 matches in a tournament.