Well, as the MSX-Pad approach is very close to the SDCC inner workings, I can see several problems here...
If I've understood right, you can specify a code starting address as well an ending one, using this I guess you can use $4010-BFFF as such addresses; then, once compiled, you would need to add a ROM header (16 bytes) as it's a raw executable (if it's a real COM executable of course); but then problems arises...
Just guessing; but the Pascal compiler (as its C counterpart) generates code ready to run in a full 64KB RAM environment; but now we want to run the code compiled on ROM; so it probably won't work. SDCC can be pointed where the RAM data goes, if HiSoft Pascal has a similar feature would be possible to generate a ROM executable on pages 1 and 2 while having data at page 3 ($C000).
Anyway, one advantage of the MSX-Pad is, as is designed to work with COM, the compiled executables are BIOS free; so you've some more freedom regarding where you uses page 0 or not, also it's very handy at choosing alternate routines, not the slow BIOS ones.
I'm sure that I'm missing a lot of things, I really think that the only man able to answer your question is SLotman. Maybe it's possible to turn MSX-Pad into a ROM development platform, that would be great as I think it's a great tool if you like PASCAL
