If you would like to vote for a specific coordi gacha to appear on the rotation then head on over here and cast your vote on the poll:
The poll will last about 3 weeks and the top four (4) gachas will be added into the game soon after the poll ends in a following maintenance. An announcement will be made listing the winning gachas which also includes Armor once the poll ends.
You can preview some if not all of the gacha sets in the page below (We suggest you View Albums for better results):
Vote as soon as possible as all votes matter!