I told a long time ago that they can add a ruleset "Rise of the Common" and I also addressed this at the splinterlands-team but they obvisiouly don't want it.
I mean really a "Rise of the Common" where you cannot use rare monsters, this ruleset had add a lot of cards even like the Rusty Android a sense, cause if you look in the Beta-Edition (+ Rewards-Cards to this time) than the most better monster (than the Rusty) are rare-monsters like Haunted Spirid, Silvershield Paladin, Cerberus and so on - to take them out of the play (in this suggested ruleset) would help a lot of common cards and add them a usecase.