Step: Supercell creates a map. (These maps dont have to adhere to the current rules, so they could have extra cc troops or defences etc. Just to spice things up.)
Step: All those who want to play in the competition take on the map challenge (couple of gems entry fee). every one in the competition attempts the challenge and must at least gain 1 star to pass the challenge and move onto the next round..
Step: This is a repeating step where challenges gets harder and more ppl get knocked out. Eventually you have to 3 star a tough base as an example
Step: The final challenge is posted. The winner/winners are crowned and get a gem reward. Winners get the most amount of gems , and then cascading down.. so that, say the top 100 players all get gems as rewards.
Step: The leader boards are updated
Step: the next tournament is announced
Its a pretty rough idea, hopefully someone can make it better?
(this follows a poker tournament pattern)