In Gen II you could take a boat to Vermilion from Olivine and that's actually how you get from Johto to most of Kanto. In the Hoenn games, you take a boat from Slateport to Lilycove and back. What if, instead of including a whole region, you could visit a port town from another region? The city or town you visit would need to have a way to get there and back, so Olivine, Vermilion, and Lilycove. Coumarine City is also a good bet. Driftveil and Canalave, too. While I don't think this is ever going to happen, it's a fun idea to think about. Thoughts?
Alls fair in love, war and video games ~ LyokoGirl5000