Is it possible to replace libraries like "exec.library" etc.. in AmigaOS without resorting to ROM/Flash replacements? ie by just running some program from the CLI.
And is there a difference in this capability between 1.x 2.x 3.x etc..?
You should have a look at the sources of
AROS for AmigaOSI think it does exactly what you want. It replaces several AmigaOS Libraries, by running a command from cli.