The problem is that I don't think people will actually 'know'....
However I found myself thinking about this too, and realised something.
When you currently run a '32bit' application in the Mojave OS, it warns you that this is not optimised for your system. It does this when an application accesses some of the 32bit OS components inside the Mac OS. Running an old 32bit OS inside the Parallels environment, I don't get any such warning. Parallels itself is a 64bit application, so is not giving the warning, and it is handling the virtualisation of the environment itself (so not calling 32bit OS components).
So my guess would be that this is going to be OK.

Provided Parallels itself retain support for 32bit OS's.
My own intention, is to make sure I backup before every new OS release (standard practice), and if necessary 'go back' if something stops the older applications from working. For me the issue is that I have to be able to support some old software that is only running on very tired hardware, and was written for 32bit OS's, and to do this I maintain old 'snapshot' virtual systems on my current machine. Some of the customers have refused to upgrade for over 20 years, and I doubt if this is likely to change soon!. I might even find myself running the current Mojave OS as a virtual copy inside later OS's, if they become non compatible with stuff I'm doing....
Click to expand...