I've homebrewed for awhile, but I'm relatively new to wine making, so it will be awhile before I have something ready to try this out, but I see no reason why it wouldn't work nicely.
A lot of bars and restaurants I've worked in would keep bag-in-box style box wine in the walk-in cooler and refill bottles to use on the floor as their house wine. Since the wine won't oxygenate in the bag from pouring, it keeps longer than a wine poured from a container.
I just finished a box of wine (franzia), and scavenged the bag for a future homemade wine. If you do this, open the box from the top because even though the flaps are glued, it is designed so that when you lift it, gravity pushes the flaps together, so it carries just as well glued as unglued). The faucet will pop right out if you insert a flathead screwdriver in between where the black plastic faucet touches the outside of the white plastic receptacle (see image below.) Once you've removed it, you can get a bottle brush in the bag through the receptacle, but be very gentle with it. I then filled the bag with warm water and dishoap and cleaned the faucet with an airlock brush before putting the faucet in the dishwasher.
My plan is to bottle (or even ferment and secondary) my wine in one gallon glass jugs, and then refill the bag as needed from one gallon jugs. (Having to finish a whole gallon from the jug before it goes bad could give me a lot of headaches.) Since the bag holds 5 liters or 1.3 gallons, I'll just fill the bag by siphoning from a one-gallon jug, and then force out the air before replacing the faucet. Once the bag is somewhat filled, the faucet can be connected by pushing the fauchet in with your thumb while pushing the receptacle toward the faucet with your fingers on the other side fo the bag. This means you can fill the thing completely, but once the faucet is attached, you can burp out any excess air by opening the faucet and squeezing out the air, and the small amount that was in the bag for that limited time is negligible compared to headspace in a bottle.
I wouldn't use bags for long-term storage or aging, since the plastic is probably somewhat oxygen permeable, but it should do well to keep already sufficiently aged wine "on tap" for a month or so (if it lasts that long.) I'm also going to place some sort of wedge in the box under the bag toward the back so I can avoid the need to tip it out of the fridge near the end whenever I want a glass. Although it looks like a 2X4 would fit in the box well, and would work perfectly if I cut it on an angle and put it in the box cut-side down, I'll probably just use a folded, white dishtowel. That way, if do end up with even a small leak, I'll know when I'm done with the box that it's time to scrap the bag if it's not otherwise obvious. I
Has anyone tried this? Any tips would be appreciated.