Although certainly no authority on the subject, my personal opinion is that you wouldn't want to do that (from experience with plumbing for ponds/waterfeatures, etc.).
The gate valve is not as good as the ball valve. I'm willing to bet the current ABYC standards dictate the use of ball valves.
R&R with a ball valve would be a better choice.
The reason NOT to do as you suggest is that it doesn't solve the problem (if, indeed, it is a problem) the surveyor points out, and also overcomplicates things.
The KISS rule definitely applies on a boat.
Bite the bullet, and follow the surveyor's recommendation (if indeed you must) and you will be better off.
/s/ Jon C. Munson II