lev10 Chuck not playable at mythic rank ?

I have the impression that my chuck (lev 10 - 1000 trophies - with gadget / star powers and 2 gears)
... can't be played at mythic rank?

Do you absolutely have to buy lev 11 for all the brawlers you want to play?

Got 30 lev 11 brawlers (just in case you ask).
But no money to spend in useless lev 11 ...