Tbh I don't find the idea of just raising the sea level a bit to be an interesting temp map. Although it could be a bit fun to see. Could be an idea for a creative map lasting a few days so people can fly around and inspect it.
However if you raised sea level, this is a problem. There would be many places, well all structures that go through sea level, where a flat, passive wall of water would exist just above sea level. Unless you would replace all air from bedrock to the new sea level with water, which would mean all caves and underground structures would be flooded.