Mix 1/3 cup water, soy sauce, honey, 1 1/2 teaspoons curry powder, garlic, lemon juice, and liquid smoke together in a bowl until marinade is smooth; add tempeh and turn to coat evenly. Marinate tempeh, turning frequently, for 20 minutes.

Combine vegetable broth, 1 tablespoon olive oil, 2 1/2 tablespoons curry powder, and salt in a saucepan with a tight-fitting lid; bring to a boil. Add couscous, cover saucepan, and remove from heat. Let stand for 5 minutes. Fluff couscous with a fork.

Heat 2 tablespoons olive oil in a skillet over medium-high heat; add tempeh and marinade. Cook tempeh until browned on the bottom, about 5 minutes. Turn and brown the other side, about 5 minutes more. Remove tempeh from skillet.

Pour remaining 1 tablespoon olive oil into the same skillet; cook and stir onion until fragrant and brown, about 4 minutes. Add chickpeas and water; cook and stir using a wooden spoon to break up brown bits of food on the skillet, 3 to 4 minutes. Reduce heat to low.

Fold couscous into the onion mixture; add tempeh. Sprinkle mint over couscous; cook and stir until warmed through, 2 to 3 minutes.