Build Your Own Vault

Instead of rotating characters, retiring characters or having pools of characters so large you can't possibly get anywhere all of which have detractors for different reasons why not make a pool that allows players to partially drive which characters are currently in play?

The numbers of characters below are just examples and obviously would be what the Devs feel work best for them but this is an example:

1)  Start with  say  4 recent 5* and 8 recent 4* characters (not the MOST recent 5*s) to keep current cards going out.
2)  Then let players choose at least 4 5* characters and at least 12 4* characters (can't dup characters in 1 or be most recent characters and unavailable to pool yet)
3)  Draw rates between 4 and 5 star characters are the same as the current pools.
4)  Point cost would probably be 25 CPs.

This is better than rotation, lets new players access old characters if they want and gets the Devs out of players pockets trying to guess what they want.