Bitburgr #5, nothing prevents it! Just wait a week or 3 before canceling. Hyatt has a similar transfer program & has been known recently to reverse transfers when the cancellation was so soon that it was an obvious workaround!
Also, Bitburgr, the Marriott rules do say "rounded to the next higher 1000."

Ideally, I wish they would set up a Gift Registry where a member could ask a bunch of friends to contribute whatever points they have toward a vacation (honeymoon ?)
Hyatt & CO already do this for cash contributions.