I've done something like this often, especially for nice dinners. The plate presentation is beautiful. I've always called it a grilled vegetable napoleon. When I make it, I layer the vegetables into a loaf pan with a bit of pesto, a small bit, between the layers. I let it sit overnight in the fridge, with a brick on top to help pack the layers tightly. After I bake it, I'll let it cool for about 5 minutes or so. This way the tomato won't be tooooo runny. Slice and serve.
If you put a small amount of pesto into the napoleon, I would suggest no sauce, let it stand alone. The flavours of the grill and basil are enough. If you really feel you want a sauce, why not do a hollandaise?
How can we sleep while our beds are burning???