Since previous mastery tokens were obtainable without much real player interactions I'd like to see something change for further masteries. Sure players have to play "well" and then they'll be able to get those tokens, It still can just depend from game to game and almost everyone is just able to easily reach mastery 7 with a champion then are decent at (Including myself). That's why I'm suggesting of making something special for the further masteries, Riot has the technology ready to make a 1v1 platform, that's why I figured you would be able to make a "gamemode" which you'd pay ip or rp for, for example 3150 IP or 400RP (Prizes could change). By paying this amount you would get a token to enter the mastery gamemode queue.
Mastery gamemode queue:
You can only queue with champions that have 1 mastery below the one you try to achieve, for example: When queueing for mastery 8 you can only play as a champion which you achieved mastery 7 on.
* For mastery 8
Best of 5, if you win those 3 games you gain mastery 8, you'd play against other people who try and get mastery 8 with any other hero.
* For mastery 9
Best of 7, if you win those 4 games you gain mastery 9, you'd play against other people who try and get mastery 9 with any other hero.
* For mastery 10
Best of 10, if you win those 6 games you gain mastery 10, you'd play against other people who try and get mastery 10 with any other hero.
Possible supreme mastery, in which you face people with mastery 10 on the same champion, if you lose you go down a position if you win you go up one. Let's say the top 200 gets a supreme mastery tag on those champions to mark their skill. This would mean having to manage more toplists and alike which might cause problems, this could also work with mastery points where people who have the most mastery points on those champions get the tags. But that would considering just playing the champions and not actually have the best skills on those champions. Therefore I think that having some sort of point system for the top players would be a better choice.
* Having people face of against other people with the same champion
* When you queue up against someone, they'll have the same wins/losses as you have at that moment, but this could be the "try if possible function" and if queue's are too long match you with any wins or loses.
* Being able to keep playing 1v1's to gain possible extra mastery or as previously mentioned for top 200 spots.
* Perhaps 2v2's for support champions who can queue with adc champions (premades or non premades)
Hope you liked it, leave any other suggestions related below.
TL;DR: Having 1v1's rank your mastery up to mastery 10, the 1v1's would be queue'd in best of N amount games.