You can do it, but you'd need to make it clear that this is an exception based on the couple's personal preference or circumstance. Most wedding traditions aren't set in stone and in China, Japan and Korea the blend between local and Western wedding traditions is often mixed to taste (in Hong Kong, for example, some people may have a completely Western wedding but still spend a lot of time picking the day with a fortune teller, or they may choose to still serve tea to the parents).
Short answer: it would not be entirely freaky for a couple in Korea to sign their marriage certificate, have pae bak and then have a Western wedding for a bigger crowd of guests a day or two later. It would be strange but not out of the question.