Do you have existing ductwork in the house/building? Do you have central air-conditioning? You might be able to add additional cooling registers to your studio if you answered yes to the above. I'm an HVAC contractor myself. You should also have adequate return-air drawing from this space, Preferably up high if your supply registers are low like on the baseboard or in the floor. The opposite if they are in the cieling. Where are you from soI know what climate you are dealing with? Depending on the size of the area, you can always add another central ac just for that section or install zone dampers with seperate thermostats for your studio and the rest of your house (if it is in your house). That way you can cool your studio independently of the rest of your house all the time. As far as dry throat syndrome, you can use a central humidifier in the winter when you run your furnace (assuming you have a central, forced-air system). Carrier is the only company that I know of that offers a system (furnace/ac/thermostat) that can independently control air-conditioing and humidity seperately. It is called the Infinity system and it is pretty darn awesome. If you can tell me a bit more about you building/home and the system that is in it now, I can probably help you a lot more.
Well, it sounds like you dont have a whole lot of options left due to space. Any split system is going to give you some pretty major fan noise right at the source and at 3 X 3 you wont get nearly far enough away. You might look into a package unit that contains all of the components in one unit that sits outside on the ground or on your roof. It can then be ducted into the desired space from the outside and the fan noise will be majorly reduced. Especially with duct liner insulation inside the duct. The downside is that you have to look at it from the outside of your house. This is why many of these units are installed on the roof. The central humidifiers that I am accustomed to are made for forced air, fuel-fired equipment. Heatpumps dont get hot enough to efficiently work one of these types and they cant be installed on package units either. You might have to go with a mist injection type but I wouldnt want to do that either inside of insulated ductwork for fear of mold forming from saturated insulation. I dont know what the climate is like there as far as humidity but here in the states (the midwest anyway) humidifiers are only needed in the winter when the furnaces run. In the summer it is the opposite. If you want humidity just open the door. Just dont let it knock you over on it's way in because it isnt very considerate. Hopefully you wont need to add humidity and cool at the same time. That is generally the case here anyway. If you did have too I guess you could go low-tech and just but a small vaporizer. I hope this helps. Let me know if you need anything else. It's nice to finally be an expert about SOMETHING around here. Lol. Take Care.