Having these 3 types of weekends would be fine to me. But probably pair the CP weekend with the featured promo of each given month, since CP does kinda encourage spending.
Have one weekend free would be fine for me also to have time to make quest, farm, kulun, etc... But since not everyone play all the games maybe even a SM -> SD -> CP could work and will be less stressed.
Anyway, if we can agree on something is that have CP every weekend isn't the best option.