I do not think you will find a window AC satisfactory as it comes out of the box. The possible problem with low humidity can easily be overcome using a portable humidifier that holds several gallons of water and that can be bought at many home centers for under US$100. However you probably will find that the AC freezes up with ice at times when you try to run it in the 50s F range with sufficient humidity. Also consider that in some situations you may need some heat if the room used can drop below the desired control temperature in the winter.
I use a window air conditioner in a room with one outside wall. However, I built custom controls for it. The advantage of the window AC is that it is easily and rapidly replaced if it fails. I keep a spare on hand.
First you need to insulate the wall well on the interior with some of the foil-bubble reflective insulation material that can be found in home centers in rolls. Follow the instructions. If there is a crawl space or basement under the floor, insulation should be applied under the wine room floor. If there is an attic, more insulation above the wine room should be used, or the ceiling of the wine room should be covered with the mentioned rolls of insullation material. Any windows or doors also should have this insulation applied.
Get the largest capacity AC you can easily handle, as the less it runs, the fewer problems you will have with ice build up or excessive water evaporation by the humidifier. The AC must be modified so it runs all of the time by bypassing the built in thermostat. Then you have to build a custom control ito which you plug the AC. I use a Penn thermostat with a very large bulb and long tube to the bulb. The bulb goes near the center of the wine room into a rack. Another Penn thermostat senses outdoor temperature and is used to switch to heatng in very cold weather. A large fan is placed in front of the AC inlet to greatly increase the air flow through the AC. The control cycles the AC as needed when the outside temperature is above a certain temperature selected by trial and error. Below that temperature, the control cycles a small electric heater with a fan as needed. When either heat or cooling is on, a fan near the ceiling comes on that circulates air throughout the room. The fan in front of the AC intake comes on with the AC, but stays on about
10 minutes after the AC cycles off to return as much moisture as possible to the room and to help prevent ice build up in the AC. The control can be built fairly cheaply with several relays, etc., but you would have to know a bit about electronics to do this.
I live in an area that has reached -10 F in the winter and 110 F in the summer. The humidity can range from extremely low to extremely high. In a situation with less extreme variations in temperature, you might get by with much less elaborate system.
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