I've read that before and seen it done a few times. For trail repairs, it does work well. In my case, setting up a mobile outfit to handle a variety of chores and work at the ranch all over the property fixing everything from cattle panels and gates, fencing, etc., to repairs on any of our dozer, backhoes, dump truck, tractors, etc.-I want something a little more solid/durable and designed for the job. On a trail or wheeling trip, pulling a couple batteries to do a repair and get back going again wouldn't be a bad thing at all as it likely wouldn't happen all the time. For constant work though, I see it as more of a hassle/hinderence than anything. All depends on your intended useage though. Like I said, that method does work well. Hell, a buddy even did this exact thing on one of my old Chev trucks years ago to a broken shock mount. You're right though-the $1200 for a premier, or even $500 for a ready welder is a fair chunk of change to pack around in the Jeep just for "stand by" useage. With the premier though, the 110v is great for using the grinder as well to clean properly before welding, or a variety of other uses as well.
Best of Luck,
Mike