Marinate shrimp with thyme, pepper, and 1/4 c. olive oil.
Skewer shrimp (2 on each skewer), cover with foil, and keep refrigerated until ready to cook.
In a blender, pure'e basil leaves with 1/3 c. olive oil, Dijon mustard, and honey until mixture is light green and smooth.
Cut tomatoes into 1/2" cubes.
Coarsely chop onions and basil.
Combine tomatoes, onions, and chopped basil in large bowl; season mixture with balsamic vinegar, 1 c. olive oil, salt, and pepper.
Brush bread slices with 1/4 c. olive oil and grill until brown on both sides.
Rub with garlic cloves and place on a serving plate.
Toss watercress or arugula with 1/2 of the sweet basil-mustard mixture and place on top of the bread slices.
Arrange tomato salad on top of the bread slices.
Salt shrimp lightly and barbecue.
Arrange 2 shrimp on top of each slice of bread, and drizzle the remaining sweet basil mixture on top of the shrimp .