Good morning,
Interesting perspective that you believe a capital heavy location would "RIP Hard".
There's a few points. Some are things people have already said, but they really need to be said again. The Tropical biomes, specifically the Tropical Wetlands have quite a large food producing capability.
What is built already comes with population. It's not a hope that population comes, but one filled with NPCs. Correct interaction and maintenance of those NPCs are going to be the deciding factor.
EP - Every multi-count that dropped in Ksana, the only Rich duchy on the map, was a a first day count drop for the most part. Meaning it's all high influence and high EP people, all planned, all aware of what was going on. It's an organization and a community that exists, interacts, and works well as a team to reach common objectives. I know this because i'm part of said community.
Some of the capital cluster is indeed in Blackheart but it too was aware of what it was doing. It's headed up by Sellayne a Duchess who is aware of the intricacies of need regarding it. Who also has the EP, and has a community who supports a trade environment.
At the end of the day this set up actually pushes a heavier economy and trade objective, although it's interesting that you'd compare Riftwood to China. I think if you are saying players might not show up, I don't think they're needed. The NPCs have needs, imagine a world where you want to be a tailor, or a shoemaker, or anything that provides necessities you have access to all of that population who needs those common, everyday items. Will importing food be hard? Perhaps but I would say that the Tropical Wetlands have plenty of answers to your concerns and every location has needs that require resolving.