If I am understanding you correctly, you are asking that if your gunsmith gets a print of your action, then you can just send a barrel to the gunsmith for him to chamber a barrel for you. Correct? So, your assumption is that all of the actions of that model on the Print are made exactly what the print says.
Top of the list of this kind of qualifications are:
Borden
Stolle
Some Batt actions, early ones were very different
These are the ones that I am familiar with.
I am not a Defiant kind of guy.
OP, sounds like you have the patience of a gnat when it comes to head spacing on a go/no-go gauge with Pre fits which is much more simple than advanced reloading techniques and advanced rifle cleaning. Perhaps more training on how to set up the Pre Fits is in order...pretty darn simple, a little time, and a little patience, Patience is the main ingredient.
Many actions listed by some do not fit the answer to your question. Many of the action companies come and go, the tried and true customs that do not need to be reworked are few.
With the liability/expense of shipping a gun, being able to just order a chambered barrel is a real plus, Shouldered or Pre-fit.