screened bottom board
a screened bottom board is likely a good idea. it helps the bees cope with Varroa destructor a little better, because the mites fall through the screen and can't climb back onto the bees. the drawer makes monitoring mite drop (and whatever else might drop) and cleaning a lot easier. cut a piece of cardboard to fit in the drawer and coat it with oil or grease or something sticky to trap mites.
on the other hand, bees don't seem to like screens much. some folks have reported heavy use of propolis by the bees to cover mesh floors. so, effective tool against varroa or one more way to annoy the bees? your call.