Good idea, thanks! The differences aren't that small, though: the NTSC build runs the game logic on 5 frames out of 6 to keep the PAL speed and timer, moves some raster splits because an NTSC frame is shorter, and all the music and sound effect frequency tables are retuned for the NTSC clock (4/5% higher).
Memory is nearly full and the raster interrupt has no spare time, so rather than merging the code I'll merge at packaging level: one EasyFlash .crt holding both builds, which checks the video standard at power-on and starts the right one, and one .d64 with a small loader that does the same.