Optionally, we can also maybe add base-executable, to initialize sys._base_executable.

I also independently advocated for this yesterday in #106045 (comment). I then realised that these heuristics are also being used for non-venv based prefix determination, and now appreciate that when running a plain CPython interpreter, all you have is the executable path (plus a sysconfig full of paths for where Python was built) and heuristics are seemingly still necessary.

If we could remove the need for the core interpreter heuristics (e.g. by only using the build config), then I think we should also remove the heuristics from venv exec/prefix determination.

On the other hand, if we don't manage to remove the heuristics at the core, then I would advocate for removing home and replacing it with base-executable, since ultimately that is what is important from a venv path determination perspective.

All of this sounds like it needs a change to PEP-405 though?

FWIW, I believe I agree with this, based on my experience computing home in uv.

Optionally, we can also maybe add base-executable

I wonder if it wouldn't be required for venv launchers anyway (if not required, it would certainly simplify various paths computations in those launchers).
If this gets exposed, it should be made public.