I think instead of people fighting over time zones and who is active in the suggestions every time it is changed, I think having each siege zone be on its own rotation would be neat. This would allow all players from all time zones to have a fair chance at besieging based on IRL availability.

Have it be on weekly/monthly schedule would let players know when the local region is going to be available ahead of time.

I just think that this is a cleaner method for everybody.