I'm not an economist, but I've been thinking about basic income and Silvio Gesell's demurrage mechanism for years now. I've come up with a currency simulation that employs both basic income and demurrage. You can play with it here: https://democratic.money

Now, I think that Gesell meant demurrage as a companion mechanism to money creation. The main goal of demurrage was to encourage circulation in a real economy, running in a real place where people had no currency alternative whatsoever ("spend or watch your money rot"). A side-effect was that it also maintained a constant supply of the currency: if you create currency at a fixed rate (X units every T time interval), but destroy a percentage of it (a form of negative interest on the money itself, wherever it may be), then if you do the math you arrive at some constant total money amount in circulation. Which is essentially what Bitcoin arrives at, except Bitcoin has a 0% demurrage rate and a 0% money creation rate (the mining rewards are just one long-running airdrop that uses hashpower to identify recipients).

Freicoin is a tough sell, because why buy it when you can buy any one of thousands of other deflationary cryptocurrencies instead? The demurrage rate has no real function if you are not going to use it to move a real economy. The only thing Freicoin's demurrage does is to create a perpetual mining subsidy, that is, miners don't earn just transaction fees, that is, fees from accounts that are moving money, but also demurrage fees, that is, a fee or tax from money that is sitting still and not moving.

People who lived in that Austrian town where Gesell created the local currency with demurrage had no money whatsoever. They did not have to purchase the demurrage money with other money. Instead, they sold their idle work into the demurrage currency, which itself was created by the town. The key was the ability of the town hall to create money, and to use that money to bootstrap the exchange of efforts between the townspeople. Demurrage was a mechanism applied over that created money. Demurrage by itself makes no sense.

However, I have to say that, when Bitcoin runs out of block subsidies, it is not clear if miners will be able to continue operational. It may be the case that Bitcoin is actually an economic time bomb, and to survive, the Bitcoin network will have to change its block subsidy function to either demurrage (to regenerate the block subsidy indefinitely) or get rid of the fixed supply paradigm (e.g. Dogecoin, present Ethereum, etc). But so far the market cap of cryptocurrencies in general are still catching up to the fact that physical commodities such as gold are no longer the only game in town for "wealth storage." Current estimates go as far as assigning 100 trillion to the entire cryptocurrency market, which would give Bitcoin 50 trillion at its current market share. That ballooning in valuation is diverting attention from the economics of fees versus the economics of block subsidies (a 0.01-Bitcoin block-subsidy is worth 2.4 million dollars if the Bitcoin market cap reaches 50 trillion).

So, Freicoin's use of demurrage, when applied to the current crypto market of wealth storagem and not to a real economy which needs money creation to function, is actually a solution to the miner incentive problem. Freicoin's demurrage is actually a competitor to blocks giving a constant block subsidy such as Dogecoin, Ethereum or even things like Reddcoin (which gives percentages of stake balances, i.e. percentage-points inflation just like fiat currencies). By finding an ideal demurrage rate which is completely unrelated to the rates that Silvio Gesell developed (e.g. 12% a year), Freicoin can provide an unique solution to the miner incentive problem, and leave basic income--which relies on identification of individual people, which is a really messy and difficult problem--to other projects (such as the one I'm working on).

In my search for a demurrage-rate parameter for wealth-storage economies, I arrived at things like 0.1%, and 0.25%, 0.35% and even 0.5%, and at most 1%. The order of magnitude for that kind of fee is from the economics of "negative interest rate investments." They exist: some central banks and governments issue strange bonds that are worth a bit less than what you purchased for. You get a fixed negative interest rate. They have some purpose that I forget what it is all about (you can look it up on Wikipedia), but they do definitely exist. Moreover, the "robin hood tax", which is being considered in the US and that was already applied successfully in Brazil, hovers around .25% and .35%.

Hope this helps.