Fair. But note that while not a "compiler kit", VBCC has front/backend separation. This is why I mentioned it. Of course, as it isn't open source, third party

Fair. But note that while not a "compiler kit", VBCC has front/backend separation. This is why I mentioned it. Of course, as it isn't open source, third party backends/frontends are unlikely to occur. Fortunately, despite not open source, the code and documentation can still be studied.