That just seems like a very bad way to even think of proposing to someone, but truth be told it is practical. Ring sizes for people do change with time, and an engagement ring is forever. So rather than have trouble with your precious ring, how about just using an adjustable one? Active Wedding Ring by Jeff McWhinney is designed for men, and includes a hinged mechanism similar to watch straps.
The design is intended to make it easy to put on and remove the ring, and to stay out of the way of activities like sports, work, or something as simple as putting your hand in your pocket. Priced at $825.