Making mastery points meaningful

An idea is to lose champion mastery points if they're reworked.

If a champion gets Full gameplay update you should lose all your mastery points or huge flat amount of it.

If a champion gets single ability changed or something like that assasin update, you should lose half of your champion mastery points and a flat amount of it if youre level 7.

Also making those champs available to earn a chest again through the season.

Sorry for my english, im just an eastern europe guy.