I've got a couple of these bags, and they were definitely built for abuse. They're routinely used to haul gear to Everest basecamp on the back of Yaks. I think they can take the tender mercies of the average baggage handler. I've used them myself for mule trekking in the Cordillera Blanca, and have used them on quite a bit of international travel.

It wouldn't even occur to me to put them inside another bag for protection. They're very tough.

As for lockable - the ones I bought many years ago weren't lockable. You could put a lock through the zipper pulls, but that's not the same as having holes on the zipper itself.