Halloumi and roasted vegetables is the halloumi sandwich with the salt problem answered by moisture. Grilled halloumi on its own is firm, squeaky, and emphatically salty, and across a whole sandwich that single register tires quickly. Roasted Mediterranean vegetables, courgette, aubergine, peppers, red onion, do two things at once: they bring a soft, sweet, slightly charred counter to the dense salty cheese, and they carry their own roasting juices and oil that sit where a sauce would. The defining character of this build against plain halloumi is that the vegetables, not the bread or a condiment, are the thing that makes the salt edible across the whole sandwich, and they read it as Mediterranean rather than as a cheese sandwich.
The craft is controlling that same moisture so it helps rather than wrecks the bread. Roasted vegetables release liquid and oil as they sit, so they are roasted hard enough to drive water off and concentrate rather than steam, and they go in cooled or warm but not wet. The halloumi is seared thick and built in hot, because the cheese still has its clock on it and still goes rubbery cold. A sturdy bread, ciabatta or a robust roll, is chosen because it has to hold a heavy, slightly oily, two-part filling without collapsing, and a thin layer of pesto or hummus on the crumb both seasons and waterproofs against the vegetable juice. The balance the build is reaching for is char and salt from the cheese against soft sweetness from the vegetables, with the bread sturdy enough to keep both in line.
The variations move the same idea around the Mediterranean. Add pesto and it sharpens green and herbal; swap in hummus and the spread does structural work as well as flavour; a balsamic glaze pushes the sweet-sour against the salt harder. Plain halloumi with only a lemon or a chilli sauce is the leaner parent that leaves the vegetables out entirely. Each of those is its own sandwich and deserves its own article rather than being crowded in here.