If your horse will poop in a bucket that should make stall cleaning really easy. If you turn them out during the day and only bring them in at night why don't you just keep water for them outside and let them out to drink in the morning? I have had horses in dry pens before and just led them to water twice a day and they did fine.
There's nothing like the Rockies in the springtime... Nothing like the freedom in the air... And there ain't nothing better than draggin calves to the fire and there's nothing like the smell of burning hair. -Brenn Hill