Welcome to CS You can keep most things in the dry cabinet, but for our body, not recommended. You need to have a rather huge cabinet & have to apply lots of moisturizer on your body. Just take daily baths
flash also can. best to remove the batteries before storing the body or flash into the cabinet. you may be too busy to shoot next few weeks,who knows? as far as i know, no camera equipment can't be stored in there.
your dehumidifier mechanism will work on to reduce the moisture. of course la, you don't put a pouch or strap drenched with rainwater or other liquid straight into the cabinet. the hygrometer indicator will tell you the optimal humdity level in there. you can't have total dryness also, otherwise it could affect the rubber grip of your cam.