well it's possible to do but only in part :/
if you load a tileset of light in BG0 when player moves the tile follow player, not remain in the same position...
if you look BG1,2,3 are updated every time we step, BG0 no...
there would be a way but it would be very difficult and complicated:
-make a routine asm always active depending on the value of a variable the routine will be active or not
-if the variable has the value set in the routine load the tile of light in BG0 else do nothing
-when load tile in BG0 control in offset of key press 4000130 the direction of player
if it goes down then ec...
if it goes up then ec...