So you are declaring all the millions of line of pre-5.8 Perl that used signals [...] not wise

No. Where did you get the idea that it was possible to turn off safe signals pre 5.8? I can't speak as to how wise it is to do something impossible.

So you are declaring [...] all the billions of lines of C that still use "unsafe" signal handling, "definitely not wise.

No. What makes you say that all C code uses unsafe signal handling? The Perl library pre 5.8 wasn't signal-safe, but that doesn't mean that C code in general can't be made signal-safe. Perl 5.8(.?) is an example of such a feat being accomplished.