If they can pay for it and those that are paying are willing to accept that cost even if its a net negative, everyone participating was willingly went along with it so I don't see the issue there

But that's not likley how it would work, it would be inflation and taxes that fund it and many would disagree. Even if you are saving in Bitcoin, you're still going to part of it in one way or another, unless you leave that country 

 Wouldn’t you just buy bitcoin with it? 🤷‍♂️ 

 I would yes, and once prices adjust upward for this new currency supply we just go back to the UBI amount not covering your living standards