What if the S6 preseason map testing cup determined the map (not maps) to potentially be added in S7, instead of S6? The map could be run in pugs and scrims during S6 so that people were used to it and ready for it when it came out.
You could even run a fan-voted Invite Allstars showmatch on it before invite grand finals, like how CSGO does showmatches on potentially new maps at big events or majors (Cache remake showmatch) (Tuscan remake showmatch)
This could help prevent the natural dislike people have for new maps due to unfamiliarity, and provide more transparency to your playerbase, allowing you to enact your agenda of rotating maps in the pool seasonally, all in a way that's fun and community-sourced.