I think when we say "impossible" we mean "well sure any old thing is possible but there are hard limits on what's consistent and sane."

I will go read the docs in more detail but what you've just describes sounds pretty awful. Perhaps it's more just you being glib about non-cooperative actors in an environment that expects cooperatuon, but an "available balance" abstractions are a pretty reasonable thing to ask for, if only to encode natural numbers.