The main differences from a tool chain perspective, though, should be in the hunks supported. Everything else could be handled as it is today, and newlib, crt0.s, and amiga.lib could be written to run optimally on arbitrary releases. Having that magic at compile time, though, would result in much tighter binaries.
Well, some 32bit relocs could be made 16bit, that doesn't account for much in most binaries.