One idea though, maybe schedule a repeating match of the day on a weekend day that is basically this "unranked" conquest every week or every other week. Perhaps if done on a weekend day like this the player base would be large enough to absorb the limited time alternative conquest mode?
By saying this could split the player base in half in point 1, you're basically saying half the base wants it anyways. And honestly just bans would do the trick and be much quicker, at least my group doesn't really care about picks.
Saying "up to half" really, and any combination of those players being split is all bad, right?
- 10% go to bans conq, 90% stay - new mode matchmaking is BAD, old mode barely changes
- 50% go, 50% stay - matchmaking gets worse for everyone
Even as a MOTD this "mode" is more likely to be like the first situation, low play count, bad matchmaking, 5 mans vs solos, etc. But hey you can play conquest with no Tsukuyomi!
I still think the positives are minimal. Play ranked.