That's not what I'm trying to say. I'm not saying we should have a portable assembler like HLA on the PC, but a front end with an assembler capable of producing the code your intended to do.
If I do 68k then I write 68k code and assemble it, the end result would be 68k code etc.
Handling interrupt, exceptions etc... is plateform specific, you can, on the Amiga do that by using the OS or the HW registers. A portable assembler can do that because it support Amiga 68K, Amiga PPC (vasm case) so there's no problem here.