Theory: Pi'illo Kingdom's Location

Abstract
The Pi’illo Kingdom is north of the Ruined Kingdom.

Arguments

 * Argument 1: This small island (pictured) has a shape very similar if not identical to that of Pi’illo Island.


 * Argument 2: It’s said in Mario & Luigi: Dream Team that Antasma was once a regular bat, before he fed off the dreams of the Pi’illos and became how we see him in Dream Team. In the Ruined Kingdom, which is extremely close to this island, the skies are absolutely full of bats.


 * Argument 3: The Pi’illo Kingdom fits in with the whole “lost civilization” motif that the Ruined Kingdom has going on.


 * Argument 4: Pi’illo Island is reached via blimp, similar to how Dinosaur Land is reached by hot air balloon. Assuming that Dinosaur Land is in the Cascade Kingdom, they are both similar distances from the Mushroom Kingdom, making it feasible for them to travel there by Blimp.