it shouldnt be that much extra load if you cache the image
The -c switch indicates that the bitmap should be cached. This greatly speeds up subsequent references to this bitmap. If you specify -c and the bitmap is already in the cache, it is loaded and used from the cache, otherwise it is reloaded from the file. You can clear the entire cache with /drawpic -c.
That in combination with the n switch.b However this suggestion does no harm and i see no reason why it shouldnt be implemented.