The panino con ciabatta is named for its bread, and the bread is doing more of the work than the name lets on. Ciabatta is a wet, slack dough baked into a flat, slipper-shaped loaf with a thin crackling crust and a wide-open, irregular crumb full of large holes. That structure is the whole proposition: split horizontally, a ciabatta is not a soft envelope that compresses around a filling but a sturdy, chewy, slightly elastic carrier with a crust that holds its shape and a crumb whose holes both drink up and trap an oil-dressed filling. The sandwich is built around what that particular bread can and cannot take.
The craft is matching the filling to a high-hydration crumb and a hard crust. Because the holes will soak, ciabatta suits things dressed in oil rather than things that weep water: cured meat, a firm cheese, grilled or marinated vegetables glossed with olive oil, the oil settling into the open structure instead of pooling and softening it from the inside. The cut faces are often warmed or pressed lightly so the crust crisps and the crumb sets enough to keep its bite under the load. The chew is deliberate and is part of the experience, which is why a delicate, fall-apart filling is the wrong choice; the bread asks for something with enough presence to be eaten through a crust that resists. It wants to be filled close to eating, since even an oiled crumb eventually yields and the appeal is the contrast of a crackling shell against a soft, holey interior.
The variations are essentially every regional filling poured into the same loaf, which is what the rest of this catalog is for. There is the cured-meat build, the grilled-vegetable build, the firm-cheese build, each a different larder met by the same open crumb. Each of those, and the wider family of breads named for their own shape, follows its own logic and deserves its own article rather than being crowded in here.