I've expanded my nuc production, but, instead of building more nucs out of the usual 3/4" thick lumber, I used 15/32" 5-ply plywood. I use my refurbished RAS (radial arm saw), to outrip four foot wide strips of the 4' x 8' plywood sheets, to 19-1/8" wide, then reset the blade to cut the nuc side pieces, either 6-5/8" for mediiums, or 9-5/8" for deeps. I don't use wood for bottoms or covers - instead I use a combination of wax coated cardboard (for some bottoms - stapled on), or #8 hardware cloth and foamboard, and black poly / small towels / thin foamboard sheets for covers. I just slide the covers back a crack for entrances.
This way, I can grow nucs in one set of these boxes, and build another set, to transfer them into, so the customers can transport their nucs in and permanently keep another set - they're very economical. They can also bring back their used plywood nuc boxes for refills. For the transport plywood nuc boxes, I staple a double layer of cardboard for the bottom, capture and cage the queen (to help keep her safe during transport), and staple a piece of #8 hardware cloth, about two inches wide, to each top end of the nucs, for ventilation, and staple through it and into the nuc edge and the two outer frames - to help hold them from slapping/shifting during transport. On the top of the nuc, I then staple a clean white shop towel/rag, between the two sections of wire mesh. It helps reflect any sunlight off of the combs/bees, keeping them cooler, and if the trip is long or the nucs need to wait much for the customer to arrive, it can be wet to provide moisture to the bees, and they can be stacked, cris-cross without interfering with their ventilation.
I haven't painted any, yet, though I'm thinking about doing so - I would probably paint the more permanent ones, to make it easier to sort them.
I don't really have cold weather, so I can't address that issue, of course. But perhaps a 1/2" thick piece of foamboard, or thicker, could be firmly attached to the outside surface, using construction contact cement (like Liquid Nails), or other appropriate adhesive. I do use nucs composed of thick foamboard, with an inner layer of aluminum, for queen cell builder colonies. Apparently the insulation helps the bees to keep it warm in cool weather and cool in hot weather.