"msiexec /a" does not install anything - it converts the MSI into a source layout for lazy network installs. It is, and always has been, completely unsupported as an approach to installing Python, and we are under no obligation to maintain it.

Copy-pasting the install folder after installation is also unsupported. We obviously can't stop you doing it, and at times it is the best way to achieve certain things, but it is not supported and we do not have to make it work better.

The /layout command is intended for full offline installs: it downloads all optional packages without evaluating any conditions and puts them in a location where they will be used later without redownloading.

You've always been able to use only a single micro version of Python at a time when installing it. That has not changed (and will not, as it's by design). We have added new package formats that do not install the full development kit, and it sounds like the nuget packages (a.k.a. zip files by a different name) are perfect for you.

I have no idea what the "-d" suffix is, unless you mean the "_d.msi" modules which contain different files from the non-"_d" versions. The internals of the installer are just that - internals - but FYI there are typically 3 installers for each component. For example, "exe.msi" contains the files related to launching an interactive shell (including licenses, shortcuts, and icons); "exe_pdb.msi" contains the PDB files associated with files in exe.msi; "exe_d.msi" contains a debug build for those who are debugging native extensions and want consistent build settings between Python and their extension.

Your criticism of the *hypothetical* single MSI installer doesn't make any sense, since that installer does not exist. I included those points to show what restrictions would be necessary to avoid any such single MSI installer breaking users who would prefer to use the EXE installer.

There is no bug here, so I'm closing the issue.