Most high light plants grow taller, and will shade your lower growing plants. Mosses take a long time to kill and grow, the high light plants usually grow faster, and will shade the mosses before they get a chance to die.
I have actually made a plexiglass cutout, which I then frosted with my sandblaster, to resemble leaves from tall trees above. This casts a shadowed light where my moss only plants are. I also selected mosses which were growing in direct sunlight, so I know that the plants are sun tolerant, or that they grow faster than they die in the full sun.
If you choose a nice medium, then your higher demand plants will grow slightly stunted, and your low light plants may just thin out... I don't think that you will kill off all of your plants. (Moss, I have found out, is more sensitive to soil conditions than it is to light variation. Some can live for years in improper setups, then just die suddenly.)