We frequently do split stays so at 11 months, I book our stay at our home resort in segments. I usually book a 7-night stay in blocks of 3 nights and 4 nights. That way, at the 7 month window, I can switch any or all of it and I can waitlist part of it too. Once a stay is booked, it cannot be broken up later unless the availability is still there.
The TLDR version is you do not want to waitlist for a portion of a reservation. You risk losing the entire reservation because MS will replace the current reservation with the waitlist.