The hitch once built would be a breeze to drop on and off.
I get the issue with backing up the wagon style trailer. I was just thinking no tongue load is all.
Now if your building the trailer yourself brakes isn't to hard
For brakes I'd take a look at the hydraulic drum options at Northern tool, and decide on how heavy you need that rating to be. then hunt eBay for a deal
now you could use a surge or I'd personally plumb it into a set of remotes with a relief and a ball valve for locking them on.
I'm not to good with the quick paint drawings but you get the idea
Check to stop the reverse flow
Ball to lock them on
Relief to limit pressure to the cylinders i doubt they can take over 1500psi (I'm not sure), start as low as you can and slowly adjust up.
Joe