I've thought about this issue for my #1, and plan to install 2 aluminum handles on the sides. The #1 doesn't weigh that much, but it's awkward to lift. I plan on getting heavy-duty handles from Lowes, and then mounting them by drilling holes through the sides and using stainless steel machine screws and cap nuts. Of course, flat washers on the inside. The stainless skin and interior, sandwiched with the insulation, should be strong enough to carry the load easily. I'll let you know how it goes - and post pics!
As for the #3, I would probably go with two handles mounted to the top of the unit in the same fashion, except use the large-diameter "body" washers on the inside. I just can't imagine short-duration lifts causing any deformation of the double-wall skin...these things just aren't that heavy. It's not like you're trying to lift them fully loaded with meat.