Maybe instead have a command called "P<0/1>" that turns on a pixel-accurate mode, and when P1 is found it will make all move character commands by pixels. And it would do this until P0 is found.
Or, maybe "P" (for pixels) when you want pixel-accurate moves, but "T" (for tiles) when you want it to move by 16 pixel each time.
Or you could do for each pixel direction command:
"PU[num pixels]"
|
"PL[num pixels]"<-- -- >"PR[num pixels]"
|
"PD[num pixels]"