In a large bowl, whisk together warm water, yeast, honey, and 1 tablespoon olive oil; let sit until foamy, about 10 minutes.
Add the 2 1/2 cups flour and 1 teaspoon salt; stir until a sticky dough forms.
Turn the dough onto a floured surface and knead, incorporating up to an additional 1/2 cup flour, until smooth and elastic, a few minutes.
Rub the bowl with a little olive oil, place the dough inside, turn to coat, cover with a towel, and let rise in a warm spot until doubled, about 1 to 1 1/2 hours.
Preheat the grill to high. Season the chicken breasts with kosher salt and pepper and brush with about 2 tablespoons of the BBQ sauce.
Grill the chicken about 5 minutes per side, until an instant-read thermometer registers 165°F; remove and let rest 10 minutes, then chop.
While grilling chicken, place corn and green onions on the grill: scallions 2–3 minutes until lightly charred, corn 10–12 minutes turning occasionally; then cut corn kernels from the cobs and thinly slice the scallions.
Grate the cheddar, mozzarella, and parmesan and have the chopped chicken, corn, and scallions ready.
Preheat the grill to 450–500°F for cooking the pizza. Generously dust a pizza peel with flour and coarse cornmeal to prevent sticking.
Punch down the risen dough, shape it on a floured surface into the desired pizza shape with a rolling pin or hands, then rest briefly under a towel.
Transfer the dough to the prepared pizza peel, quicken rolling if needed to fit, and spread about 1/2 cup BBQ sauce over the surface.
Scatter a layer of the grated cheeses, then top with chopped chicken, grilled corn, sliced scallions, more cheese, a drizzle of additional BBQ sauce, and about 2 tablespoons ranch dressing.
Slide the pizza onto the grill grates (lower the burner directly under the pizza to low), close the lid, and cook 5–8 minutes until crust is golden and bubbly, rotating as needed for even cooking.
Transfer the finished pizza to a cutting board, sprinkle with extra parmesan, drizzle remaining ranch if desired, and top with chopped chives, fresh basil, cilantro, and quick pickled onions; slice and serve.