We were able to do this on our last cruise. We wanted to try out late dining, but after one night it was clear that it was not for us. Our head server was able to work some magic and we were switched to early dining the rest of the cruise. The ship was pretty full so i know we were really lucky they could make it work. As a bonus, we liked the service team we were switched to MUCH better.
If I recall correctly, they broke out gratuities for both teams, so there were two names under each role. It was a little complicated because I wanted to add extra tip for just the second team so it took some doing because at first I could only add extra tip for "Dining Room Server", for example, and it would have been spread across both "Dining Room Servers" rather than just the second. Guest services made it work though.