Sanke 1/4 Slim Fermenter Question?

I've got a 1/4 slim keg that I may try using for a fermenter and would like some expert input. I also have a spare sanke coupler. My thought is to get a Kegman retainer replacement kit, pull out the probe and cut it pretty much off. Once good and clean, then put it back in using the Kegman kit. Being that I already have plenty of beer & air line, I thought about just hooking up a sanitized beer line to the beer out port on the coupler, and capping off the air in port, and running the length of beer line into a bottle of water/sanitizer. I will be doing basic 5 gallon extract batches to get started, so I would think that there would be plenty of head space to avoid using a large blow off tube.

The other factor I am thinking of, I already have a second probe out of another keg, I could trim it by an inch or two, and put it in once fermentation is complete, and then transfer with CO2 into a corny. The 1/4 slim size will fit in my kegerator much easier than a ale pail, and the idea of a glass carboy just looks like it is asking to get broken.

I like the idea, but since the connector on a Sanke will fit a 2" TriClamp, why not just get a TriClamp with a 1/2" hose barb and call it good? Seems like it would be easier to maintain, clean, sanitize, and take up less room. You could still do your idea about the spear as a transfer tube.

My thought by using the coupler is that once fermentation is complete, I could pop off the coupler, and throw the 1/4 barrel would already be completely sealed. Also, it would avoid having to buy any additional hardware.

I know a couple of brewers who ferment 10 gal batches in 1/2 bbl sankes just like you describe. They leave the spears intact so that they can easily transfer with co2 counterpressure. They just trim a tiny bit off the spear to avoid the yeast cake. If you leave the spear in, the airlock or blow-off needs to be on the gas in port.

I ferment in 1/4's all the time, just pick up an Orange Carboy Cap, dip it in some boiling water for a minute to make it stretchy and stretch it over the top of the sanke keg. You can also pressure transfer with a racking cane and CO2 with the caps.

I have been investigating this a bit more all day, and two options have come to mind.

Option 1: as it turns out, the Triclamp fittings are easy to get ahold of, they are standard issue in the dairy business, and my cousin is a dairy supply wholesaler.....and just down the road. I could fabricate up something pretty easily this way with just a clamp and a cap. I am thinking just drill a hole in it properly sized for a air lock gromet.

Option 2: Go the probe/coupler route, and leave the probe in tact less a couple of inches, and hook up the air lock to the CO2 side. I've been playing around with this all day, and it appears that you can just reverse the anti backflow valve, and it will make a perfect air lock without having to use a hose or bucket of water. I will probably still use a tube into a bottle of water just for the sake of seeing the activity.