I do this! Interesting to see someone else advocating the practice. In my open source development I start work on a retro machine running Snow Leopard, specifically to be able to generate authentic retro binaries that'll work anywhere, and then I have a process to port to modern MacOS and signed Apple Silicon binaries, but the machine's a M1 Studio on Monterey and building for 11.1.

My worry is that they'll kill signing for people who aren't updating, though that shouldn't be a factor. I would have to simply get another machine to port to, because I don't trust that changes they make are always going to be good in any sense.

There might be a window for computing within which it's good: I find I'm not worried about adding new Linux machines and architectures to build for, but my Windows builds are 32 and 64 bit on Windows 7 with no attempt to modernize the build system, and I've got that two-stage Mac build process where it starts on a time capsule machine not connected to the internet, and continues on the M1 running Monterey. I'm anxious for the day Apple requires you use stuff that's constantly changed out from under you. I don't work like that.