In a large bowl, layer in order: the watermelon, strawberries, tomatoes and basil.
If making in advance, cover and refrigerate up to one day ahead.
For the Balsamic Vinaigrette, whisk together the balsamic, mustard, maple syrup, salt, and olive oil. Reserve in the refrigerator until ready to serve.
When ready to serve, stir (or shake) the balsamic vinaigrette and add to taste. Then season the salad with salt and pepper, and toss well. Add crumbled blue cheese, and lightly toss once more.
Serve and enjoy!