> How will this interact with EnvBuilder.install_scripts() (which explicitly states that it performs textual substitution)?

It won't, so that would have to change as well. As you mentioned, Paul, I don't know who even uses the functionality through a subclass, but since this is a security consideration I think it's worth changing.

> Is it?

Sorry, misread what you were asking. You're right it's not stored, but it can be worked out in other ways, e.g. from the location of pyvenv.cfg or Activate.ps1, etc.

> So there could be code changes in venv too.

Yep, hence making the issue now so that others talking about adding more substitution ideas know that there's talk going the other way and removing the substitution abilities.

> This would be a great contribution from a PowerShell expert, and might be worth advertising (Twitter) for one.

Already have a co-worker interested in working on it.