After Luke, right now we have a total of 32 3* characters, of which 20 are in circulation, 12 are vaulted. As more characters are introduced, if the circulation population is to remain at 20, the vaulted population has to increase. At some point of time, why not create a “Token for Vaulted Characters”, that only award covers for those vaulted. And have this as reward for just specific tournaments. As the vaulted population gets larger, the probability gets lower for specific covers, and the token becomes “less desirable”, but this is the whole point.
Actually, Lightning Rounds seems the best place to have this new reward token. With not so appealing rewards, the big sharks may stay out, and transitioning players can rough it out among themselves for Iso and vaulted tokens, which are exactly what they really need. Mature rosters can better spend their time chasing events rewarding the normal tokens with newer characters. And no one has to wait or stockpile tokens in hope of waiting for specific characters to rotate out next season. I think this helps to address a few issues we have currently, and provides a long term solution for cover rotation.