Taking Africa as an example, the African nations depend more on imports than exports, if there is no fiat devaluation the developing and the underdeveloped nations are using to protect their foreign reserves, they would lack more than these days. Assuming if only decentralized currencies are existing, the developing and underdeveloped countries will use all their decentralized assets for import and nothing will be left, this will be a great suffering while developed nations will be enjoying while the less developing countries like African countries will depend on them.
It will not happen like that, and devaluation is not a solution long-term either.
Imports in a country are the results of people's needs, if they can't afford those they will not import a thing, but they will also need to work in order to have enough money for those goods. The moment you pay for something it doesn't mean that the money evaporates from your economy, you have bought a good worth that value, and the same is true for the exporting partner, he has received the money but he has spent a lot on the needed materials and work. A trade deficit is not always a bad thing, and if the country is to be left without money it would somehow magically need to stop every single person from working or making anything of value, long before that the trade deficit will be gone as they will not be able to buy anything.
At the same time just devaluating your currency will at one point reach a dead end, you might be able to keep all the currency in as people would be too poor to travel, you would encourage tourism as things are cheap but there isn't a single country out there that is self-sufficient. And this is far more problematic exactly for developing nations, without purchasing power you are unable to import the means of producing the stuff you want to export, you're cornering yourself with your own policy. Think of Zimbabwe, because of devaluation Zimbabwe should exports a lot of stuff, right? Well, despite that Zimbabwe still runs a trade deficit, and when your currency is worthless you need to prop it, and this can only be done with a strong economy or by, trying to print more money which leads to the situation we all know of.
One more thing, let's assume the developed nations will have to get their hand on all the coins, how would they be able to run a trade surplus when the others have no money to buy stuff from them? They got their hand on all the money but once that value is not circulating anymore it is useless.