Hopefully there aren't some baffling limitations to the new terraforming/island customization. For example, I sincerely hope there is no arbitrary limit as to how many bridges you can have in your town, or how much water vs. land. I saw someone here (or was it reddit?) post an idea that seemed like Amsterdam/Venice/St. Petersburg with canals and bridges dominating the layout; I'd love to make something similar seeing as how those are some of my favorite cities IRL.
If not, I'll work with what I got, I just recall being annoyed that every idea I had in New Leaf was quickly shot down by Isabelle.