There is no reward for being an omnicrafter, no.

But, there are rewards for being a crafter. And, a gatherer. Simply make (or gather) everything once. Fill out all those check marks in the logs that have them. You’ll get achievement rings for ARR near completion, and special tools for HW and SB near completion. We are not at the point yet that those achievements are available for ShB yet, but if history is any guide, they are coming.

That being said, the only reward for hitting max level in combat jobs is an achievement, that usually comes with a crown, but at 80 comes with a mount. Being a max level omnicrafter gets an achievement, which comes with a title. So, you can have said title on full time, where the combat jobs you have to either have the crown as part of your glamour (and hope someone notices) or be riding the mount; DoH/DoL classes can be on display full time.