You can fry up some catfish outside on the side burner of you gas grill. Fried catfish smells great when you are hungry, but not so much three days later.
I bought a 15.25" Lodge skillet around a year ago to use as a roasting/broiling pan. It's a heavy mother, and/but I love it. I don't do much cooking outdoors and I don't use it on my ceramic cooktop, but it's great for what I use it for.
I have a ridiculous dream of someday owning Lodge's biggest skillet (17").
I have no reason to own such a big skillet; in fact, I doubt it'd fit in my oven. Some guys want to have the biggest, baddest truck on the block, but (call me crazy) I want to have the biggest, baddest cast iron skillet on the block.
Standard sizes for cast iron skillets are usually around 10" (10.25" for Lodge) and 12". A 17" cast iron skillet would be monstrous. It comes without a traditional handle because no one could hold the skillet, full of hot food, with one hand. Lodge's smaller skillets feature the handle you're probably thinking of.
Using it as you would a Dutch oven would be problematic but not impossible. First, it has no lid, so braising and stewing would be impossible without some sort of makeshift lid. Also, it would have huge heating and evaporative surfaces. Basically, liquid foods would evaporate and begin to burn very quickly due to the huge width and shallow depth. This pan would be at its best when used as a large griddle with a wide flame. You could cook up a huge mess of eggs or sear a mountain of steaks at once.