Well, there are currently polls out there. Perhaps we can add polls specifically for events? I know World of Tanks has recently done a poll event where they polled players which tank they wanted to see boosted. The players voted on their tanks and World of Tanks had an event for the winning tank. (Namely, the Interactive Special which resulted in the T29 tanks being on discount for a week to those of you who play WOT) So maybe we can have a specialized poll for "What room do you want boosted the most in our next event?" It can be that the most popular room gets the most boosted days in the event, and it will go on ranking. For example, voting between Night Battle, Skirmish, Great Battle, Great Battle 2, Blitzkrieg, and World at War. This will prevent it from always being Great Battle, but at the same time the Great Battle lovers will be appeased. Say the places come like this:
1) Great Battle
2) World at War
3) Blitzkrieg
4) Night Battle
5) Great Battle 2
6) Skirmish
Then Great Battle could be boosted for a total of 7 days, World at War for 6 days, Blitzkrieg for 5 days, Night Battle for 4 days, etc. They can be mixed and matched, like how World at War and Blitz are boosted on the same days sometimes, or each battle can have its own day. By the way, if each battle has its own day, the numbers will work out so that the event will last exactly 4 weeks. (7+6+5+4+3+2+1=28)
Going further, we can have the days be arranged like this. Each number denotes the ranked event:
1-2-3-1-4-2-5-1-6-2-1-3-4-2-1-3-5-2-1-3-4-1-2-3
So that the events are spread relatively evenly.