Hi,
I'm currently starting my 3rd generation of hutches, there are always things to improve.
Wood: I just recycle pallets, didn't have any problem with that wood in 6 years. Parts that most likely will be damp most of the time get soaked with a mixture of sunflower and linseed oil, I heat them with a gas torch to get the oil deep into the wood. To prevent the rabbits gnawing it I paint it with deluted rabbit urine and rinse it afterwards.
Put the legs of the hutch on a solid, dry foundation - and prevent the rabbits from digging there - one of my hutches is already 10cm lower because they start tunnels at the legs until the leg sinks into the hole.
Floor: Depending on where you live a wire floor might be good for the lower level, I make wooden grates with about 20-40mm wide boards, with about 13mm slots between them. The boards are cut so that the slot becomes wider downwards. The more narrow ones at the sides/corners where they prefer to poop. Put some thought in the design so that poop can't accumulate in corners, on edges or girders.
Pans: I tried to make my own and failed, currently I'm using underbed storage boxes from ikea. Not ideal, too flimsy and brittle in the cold. For the next one I'm going to use cheap concrete mixing ponds (is that the correct expression for those 60 Liter, rectangular, black plastic containers?) from the hardware store. Cheap, durable, and easy to handle.
Hidy houses: One for each rabbit, with two entrances each (Mine ignored those that had only one hole, except when needing a nest box). And a front wall that can be easily taken out (with 2 latches, levers - I use just two bent nails to keep it in place), very comfortable for cleaning or when you need to catch a bunny. For one entrance I use a cardboard roll that leads to the level below.
Water heating: I use electric heating pads under their water bowls, works great.
Ramp/Tunnel: Since mine get garden time I will build a fixed ramp or tunnel with a door inside the hutch to let them in and out. Now I have a collapsable ramp for the upper hutch.
Lights: I still have only one hand free at night because of the flashlight, that soon will change.
Cast iron grate: They love that to lie on, about 1ftx2ft.
Nest boxes that are on one (the shady) side, so that I can access them from outside by lifting the cover.
Grass/ hay racks that can be maintained from outside, they are part of one of the doors. Mine need a cover since kits love it to climb into the racks.
Well, just a few thoughts that crossed my mind.
