You would need an addition part to step 3 for it to comply with Steinberg's license:
3a. Prompt user to sign Steinberg's "non-distributable license" agreement.
3b. Downloads ASIO SDK from Steinberg.
I recall asking the developer's a similar question some years ago. Docker did not exist back then, but I think the reply that I got is still relevant.
I asked why there couldn't be an executable script for users to download and run, which would download the necessary source code and build Audacity. The reply was, that once a working development environment was set up, building Audacity on Windows is actually highly automated and very easy - the part that causes the trouble is getting the development environment set up and working.
Unfortunately, Windows does not provide a development environment by default, so most users will need to download and install several very large packages from Microsoft, including C and C++ libraries, a compatible version of MSVC, compatible SDKs and so on. The exact steps can vary from one machine to another, but perhaps Docker could simplify this?