Just as an fyi, we are moving forward with adding this functionality, so if anyone has concerns, please let us know ASAP.
Ticketed here (with some PRs already added):
One thing I found surprising was that accession number was not whitelisted as one of the mutable properties of an order, so I added it… from previous discussion it seems clear that accession number is meant to be fulfilled by a downstream system, and therefore would need to be mutable:
Take care! Mark