Unico is not ductless, just smaller supply branch hoses off of insulated square or round main feeds under higher static pressure, thus called high-velocity systems. Definitely not a do-it-yourself installation without HVAC install knowledge, plus high-velocity training, design and layout experience. Not to mention the refrigeration tools, pumps, gas, guages and brazing torch required for proper install.

"Loft" means one big open space? Square feet means little compared to insulation, air permeability and climate. Cooling only or heat pump? Manufacturers generally all make a lot of sizes for different applications so I don't understand your problem in choosing your "system". Do you want to heat your water with this system?

I am loosing my mind or someone deleted my statement that I live on the (South) Gulf Coast! That is a very important part of many of my comments on house issues. It is obviously very hot and humid here. Your BC situation is so very different so I can't really speak the practical side of your heating issues. No, I did not install it myself. I got a guy that's been teaching at the local trade school forever as far as the local installers go. He did not have much experience with minisplits and called in a collaborator for the job. They did a really nice job running the tubes and electrical through interior walls. The house is raised over an open crawl space so I don't have anything but the outdoor units visible outside. Now I have three whereas before I had two conventional two-ton compressors, one AH, with a gas furnace in the attic. I mostly looked into Sanyo, Toshiba and Mitsubishi. They all have advantages and disadvantages wrt operating features. I do not know your climate so my main concern would be low temp heating performance. Here if you have enough cooling in a heat pump, you can not really run out of heat. One thing I have noticed, but don't understand is that the single minisplits are more efficient and better at low temp than the multi systems. There has to be an engineering explanation or they are just a year or two ahead with the single systems and the designs will trickle over with a delay. Overall, we really like the system. It fits our lifestyle. We are out a lot, and the house has its original doors and walls intact. The inherent zoning feature should save us a lot of money over the years since we will have less expense for conditioning of rooms that are not occupied at different parts of the day and night. My systems are mounted high on the walls. It was very cold for my area when we went into operation so it got a good test. One thing that I noticed is that the programming could be better for heating. The inside blowers go to slow mode when the temp approaches the set point. This makes them good ceiling heaters. (That seems pretty predictable. I've lived in homes in predominantly cooling climates with both supply and return located in the ceilings.) Bumping up the blower speed manually solved the problem. I suppose that the ceiling fan might have done the same thing. One thing I am very glad that I did was to change the first plan to put the units at the head of the beds in a couple of rooms. I was actually concerned that the cool air would cascade down on heads at low blower speed. That might have been a problem, but it would have been even more annoying to have hot air on the face in the "winter". Keep in mind that you can mix and match. If I had not gone entirely with minisplits, I would have had a regular forced-air system and installed one mini in the rear utility room. The duct to that area originated in the attic, ran vertically down a chase through the house and under 2/3 the length of the house to three registers in the floor in that room. It was a weak point to keep in a main system. The expense of mixing systems like that might depend on how capacity breaks down in choosing a "main". Finding a good installer who is experienced with minisplits might be difficult.

You might be able to put the compressor unit on the balcony, and then feed refrigerant to a unit on the inside wall abutting the balcony. Let it cool everything, or else you have to pay for more expander heads and the plumbing. Also the heads have to drain, and I will be happy to regale you with possible issues associated with doing so. A few years ago (in NH) I had installed two Mitsubishi systems, one 4-head and one 2-head. Four of these heads are on interior walls. I think the price was near $20k to cool 2600 sq. ft. If you are only supplementing the building AC in the summer, and doing moderate cooling in the fall, you may not need a very powerful unit. I can say that the compressors and the heads are very quiet. You can hear the fan at the outdoor compressor. It is about as loud as a window fan on low. At one point one compressor developed an intermittent racket, fixed by some adjustment, when the compressor iced up trying to pull heat from near freezing humid air. They are designed to de-ice, but I think between fan alignment and ice build-up there was a bit of overlap that needed to be adjusted. You will need a hole in the wall to contain two refrigerant lines and a control power line. The lines to the compressor unit will be covered by a plastic cover. You will need an outdoor disconnect switch and power feed of 20 to 40 amperes at 240 Vac. Your balcony may be subject to a warm air breeze from the compressor unit, depending how it is placed.