Re: Ramifications
"the first thing a tech does with a PC they are diagnosing hardware issues on is to go into the BIOS and enable Compatibility Support Mode, so they can boot their super-duper diagnostics-filled flash drive ... and then changes it back to UEFI when they need to boot MS-Windows."
What OS do you have on your flash drive? I have Linux on mine. It boots into an Arch environment with all the utilities I remembered to install already present. For a while, I used the 32-bit version which UEFI could boot just fine in case I used it on an old computer. Then I tried to install some new packages and realized that hanging back had caused some problems installing and updating, so I had to choose between updating that image more frequently or just using the 64-bit version. I chose the latter and since doing so, I've found zero computers that I needed to use it on which didn't accept it.
"Older hardware frequently have firmware updates and profiles which can only be loaded using a manufacturer's program, which runs only under some 16-bit operating system"
You're already out of luck on that one. I can't boot those operating systems natively on newest hardware anyway. If I have such a device, I'd either get an old computer whose entire purpose would be running that software or I'd see if I could pass enough stuff through to a VM to make it do that. Also, while I'm sure there's plenty of hardware with such limitations out there, I question whether it's really getting firmware updates that still need a 16-bit uploader. If the company is really still updating them, that company can make a more modern firmware uploader.
"Older industrial, machine, and application programs run only under (some form of) DOS.": Again, I know it's true, but those machines tend to include their own computer. They don't just let me slot in a new computer, which is fine because the new computer can't run DOS already and probably lacks the interfaces and/or custom chips they've built into theirs.
"Techies (used to) have all sorts of DOS-based and bare-metal based diagnostic and testing programs. [...] Many of these programs were hobbyist-or small-company-written, and their functionality will not be effectively replaced by the larger software houses"
Do you have a single example? I knew a few of those tools, and they have either been replaced by something open source or they no longer do anything particularly useful because, when the author of the 16-bit version stopped working on it, it stopped being useful for problems that happened on newer hardware.