DoomYoshi, I think you're getting unnecessarily complex here. I would just have the mods (Entertainment Team, perhaps?) pick out what the next month's challenge will be. I don't think it has to be completely random.
What do you think about the following as part of your suggestion?
1. Make this a premium only perk; and/or
2. Have a link like there is for Battle Royales, but have it say "Challenge games"
The link would take you to a screen that says,
This month's challenge is to defeat 30 unique opponents on Antarctica map. Maybe there would be link to waiting games or maybe they would be premade and ready to join and/or maybe a link to the Create Game screen with whatever options are part of the challenge pre-selected.