On Fri, Jun 15, 2018 at 04:34:40PM -0700, Pieter Wuille wrote:
...
> First of all, it's unclear to me to what extent projects have already
> worked on implementations, and thus to what extent the specification
> is still subject to change. A response of "this is way too late" is
> perfectly fine.
...

The new Coldcard hardware wallet is based on PSBT (ie. BIP 174 as
published), and we consider it "PSBT Native". It can add signatures
to PSBT files delivered on MicroSD card and/or over USB, and is
able to finalize PSBT files for lots of simple cases. It already
works well against the existing BIP174 pull request.

I think the BIP174 spec is reasonable as it is, and should only be
changed in a forwards-compatible way from this point... but obviously
I'm biased.

As for your specific comments, I don't have strong feelings really.

---
Peter D. Gray  ||  Founder, Coinkite  ||  Twitter: @dochex  ||  GPG: A3A31BAD 5A2A5B10