I think there should be a terrain rule for islands. There should be some trees, shorelines, a hill or two, a lake, and other things to make it look more than just a slab of grass. For example, on bunny, there's a hill overlooking a harbor. That's pretty realistic/natural.
I like the island warp idea, for Citizens+ the optional warp would cost $50, and a percentage of that could go to the island owners? Just an idea, leave your comments below.
There could be some general island rules and the island owners could "fill in the blank" to fit their preferences. Examples: All houses on the island must be __________ (build style, like modern, traditional, medieval). Apartment buildings are only allowed on plots with _______ (something like bludsky or bobsky) in the region name. Houses/buildings made out of ________________________ (blocks such as obsidian, purpur blocks, netherbrick, gold blocks, etc.) are prohibited. Regions that are left empty, half-built, or have prohibited blocks on the exterior will be given a warning after __ (7,10, 14, etc.) days, and the plot will be forcibly taken if you are active during this time and there is no change within __ (7, 10, 14, etc.) days. Optional, depends on what the island owners want: Before a house/building is transferred to the island, _______________ (username(s)) must approve the build.
Let me know what you think.