Let the captains choose which days of the week they'd like to have be regular rumble days. They could choose between 1 and 7 rumbles dates per week. Start times would be uniform, at noon or midnight GMT. Benefits: 1. Guild members would know when to expect rumbles. 2. There would be a much larger pool of guilds for more even matchmaking with the uniform start times. I'd also suggest removing the 5 gem cost for starting rumbles, and allowing for just 3 or 4 guilds in a rumble if there aren't a multiple of 5 guilds signed up for scheduled start times.
