To the OP, if you don't back the trailer up very often to keep in practice I would do like has been mentioned, just get a hitch for the FEL and be done with it. There are quite a few company's that either make a weld on or a bolt on hitch. So much easier and faster if you don't do it often.
I know it may feel like a cop-out but it does take A LOT of practice and you have to do it fairly often to keep it there. I think you said you have air brakes on it, you can make a spare long hose to hook up to it if needed, and I do like your reasons to keep the trailer. I kept a spare 20' air line I made up with an air nozzle on the other end when I drove truck to fill any low tires with the trucks compressor.
I drove double/triple trailers with a few 53 footers thrown in for around 45 years with a smaller freight company and I could back the doubles up no problems but the triples I gave up on. It's all I could do to back the trailers with the second "dolly" up to the third trailer and I usually gave up. It was so funny to watch some of the "old guys" back up a straight truck (ok, me too), similar to U-Haul truck, after so many years of backing up a trailer it took second or two to realize the truck doesn't bend in the middle.
Actually a lot of B-trains as well as A-trains here on the west coast anyways, most of the chip trucks use them here and have seen quite a few lumber haulers use them also. Some of the chip haulers did have a lock-out to back the trailers up but it was only used to back up straight. Never drove one only talked to a few drivers at the coffee shop.