As has been noted, the Lightweight wasn't particulary light but was lighter than the normal S2/S3 SWBs, especially with all the removeable bits taken off: doors, rear top cappings etc. More importantly it was narrower as it was designed to fit into the Beverly, hence the slab sided body and unique to type axle ends.
As for a winch, you might like to consider a hydraulic one, some years ago these were popular when driven off a power steering pump which you would have to fit of course.
You need to consider when you will use your winch, hydraulic and PTO need a running engine, electric needs a BIG battery. Also worth think about where you will use it, a front winch pulls you further into trouble, a rear one pulls you out.
GMB