2D Battle in 3D World

I’m looking to have random encounters as you walk through my game world, and I don’t want to load into a separate level to start a battle. I would like the battles to look like Etrian Odyssey style or the original Phantasy Star.




And when the battle is over return to normal gameplay.

Would it be better to do it it with widgets for the whole scene? Or 2DPaper with widget overlay for the battle? Or any better ideas?