I'd recommend getting a small truck bed toolbox and mounting it on the front of the trailer (on tongue frame directly in front of deck front rails).
Store trailer stuff and battery inside of toolbox...pop out battery and connect it when needed, then put back in toolbox.
Or run wires to it in toolbox if you're feeling fancy.
Mount the winch to a receiver winch plate...weld receiver tube to front of trailer behind toolbox.
Now you have yourself a removable winch you can mount into any receiver.
My buddy has this set up on the trailer I borrow from him...works like a charm.
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