This might work in theory, but you need to realize that Lemm's code is not a simple replacement of the original drawing code. You need to modify a lot more than just one function. Adding all the checks that would allow you to have both versions in one executable and swap between them by changing one variable requires a not insignificant amount of new code, which also takes up precious memory.
Also, Lemm's code requires that the "shifts" settings for all the sprites are set to 1 in the EGAGRAPH file. This is what actually lowers the memory requirements (instead of 2 or 4 copies of the same sprite, the game only has to keep one copy in memory). So in theory, you would need a new EGAGRAPH file. The game could be told to ignore the "shifts" value (or pretend the value is set to 1 when in "shiftless" mode), but again, that means more code.
I'm not saying it would be impossible to add all this code. I just don't want to do it, at least not right now.