Preheat the oven broiler to high and position a rack about 6 inches from the heat source.
If the rotisserie chicken is cold, warm it briefly in a microwave or skillet until heated through; shred or dice as needed.
Warm the prepared cheddar cheese sauce in a small saucepan over low heat, stirring occasionally, until smooth and pourable.
Arrange a generous, even layer of Doritos on a large broiler-safe baking sheet or platter.
Scatter the warmed rotisserie chicken evenly over the chips, then pour the warm cheddar cheese sauce over the chicken and chips.
Sprinkle the shredded Monterey Jack and cheddar cheese blend over the nachos.
Place the tray under the broiler for about 1 to 2 minutes, watching constantly, until the shredded cheese begins to brown and bubble.
Remove from the broiler and immediately scatter the pickled jalapeño slices, diced tomatoes, and diced red onion evenly over the nachos.
Drizzle the Baja chipotle sauce over the nachos and serve warm.