Currently the scheduling system is alright. It has it's issues, but it's not a bad system. However I think it can be improved, especially for those players who have difficulty attending Clan Battle scheduled times.
This stems from my own issues. I live in New Zealand and clan battles in Asia STARTS at 1am for me. Cross server matchmaking is useful, as this opens up other times. But it still limits my participation to 1 Clan battle period a week due to the weird days they have scheduled CB to be, and the 24 hour reset of cross server selections. This ultimately means I can only play on the weekends, and I have to choose which server I want to play on, that being either early as hell on Sunday morning 1am onwards, or on cross server time periods, which conflict with time. Stifling my desire to get amongst it and pew pew at boats.
This can be completely resolved using a system which allows you to enter ANY clan battle time period (you dont have to select, it just tells you that NA/EU/ASIA prime time CB has begun). The system simply allows you to participate in a maximum number of clan battles per week (whatever number wargaming thinks is fair. Personally I think 3 clan battle periods a week is a good number). After all particpations are conducted you are locked out of CB until the weekly reset (say prior to the Wednesday CB periods). Then another maximum participations is allocated and CB continues on each week like so.
This would allow people in difficult timezones to participate, allow those who work throughout the week to maximise their CB experience on say the weekends, and increase overall numbers in clan battles without the selection system in play (which I think we can all agree is a bit annoying with it's 24 hour limitation).
Simple and easy.