Dang, seems like some guy that wears a white dinner blazer with black dress slacks and black Bostonian shoes to go out to eat lasagna, can't figure out how to get a piece of plate steel or angle iron under a trailer and drill four holes, seriously?
Have you recently priced paying someone to drill holes in plate steel or priced plate steel itself? Then there is the issue of a Rube Goldberg operation using a torch with dubious precision.
Cheap Chinieium mounts and winches are easy enough to find and may be good for a once-a-lifetime winch pull before they fail but, do you really want risk expensive things over trying to save ~$800? In my case, Big Tex has the press brake, verticle drill, and plate steel to make a good winch mount for a reasonable cost out of steel appropriate for a good high-torque winch.
Just have your butler make a few phone calls to metal shops in your area. Flip out a grand and I'm sure some guy with some common sense can mount a cheap Bad Lands winch on a trailer which is all anyone would actually need. But, if your dinner crowd would embarrass you for a less expensive winch, buy a Warn, top of the line model with synthetic line and a variety of attachments, after all, there is an image to maintain with that trailer with this crowd on line.
Sorry, but there is value in a good-quality winch that will still work after being rained on and caked in mud. If you only need to use it once and know when that pull will be needed, a cheap winch 'might' work.
Just say'n, anyone smart enough to pass a driving test should be able to figure out how to operate a drill and wrench and should be able to figure out how to bolt a winch to a trailer. Make sure you don't mount it backwards!
Assuming you don't have a real shop with mills and drill presses, who out here can hand-hold a drill to put 4 holes in the right place in a piece of plate to bolt up your winch? Then there is the quality of the welds to attach this plate to your trailer so that you won't bend or warp your trailer with a hard pull.