I've got one of the little cylindrical fridges. I've used it to put my fermentor in a few times as a standard brew fridge, but I have definitely thought about just fermenting in there directly.
Its my personal opinion that people freak out about scratches etc in their fermentors far too much and unless you gouge the crap out of it, I don't see that you would have much of an issue at all sanitising the inside of one of those fridges, even if it had been used for other things.
Not sure about the ones you a talking about, but mine just has a lid that sits on top and seals under its own weight. It gets airtight enough so that the fridge pulls it on tight, so I think that would be good enough. You wouldn't need an airlock, just sir the lid on there and when the pressure builds up enough, the gas will leak out, when its too low to leak out the lid will sit in place and seal.
The seals would be the thing that would be hard to sanitise well, but they also would have no direct contact with the wort, so a bit of cautious effort would see you right.
I wouldn't however be drilling holes in it, I'd go for siphoning out. BUT ... if you could work out how to safely drill a hole in it and installed a nice rotating racking arm and a fridgemate.... then you would have a lovely 50ish litre, self cooled, stand alone fermentor.
If you already have one, I say give it a go. I might well do a kit beer in it first in case it all goes pear shaped. Mine is currently used as my keggerator, or it would probably already be serving duty as a fermentor. If you don't already have one, well, they aren't exactly cheap, but if you did buy one, as I said, a normal fermentor will fit in there. If you are using one of the taller narrower ones, they will go in with a fermentor tap on, When I used my Coopers fermentor I had to bung up the tap and siphon out because it was to wide with the tap on. So worst case scenario is that you get a spare fridge that can be used as a single fermentor ferm fridge.
Thirsty
