If you're going to use a key space in the trillions, and partitioned and sparsely populated rather than sequential... isn't that just reinventing what the UUID already is?

A UUID is just a 128-bit integer, with creation algorithms designed to partition that space by things that already have enough entropy to need no further synchronization.

What you're proposing sounds like roll-your-own-UUID, which might be similarly inadvisable as roll-your-own-crypto.