I think a single player puzzle solving 1st/3rd person game is a good mini project to see if this team is able to create anything.

The models created for this project can be used in RPG/FPS like games if the style fits.

To start with an RPG you would need (technically) inventory, text engine, ... which is complicated enought
But more important: a great story and a story teller who is able to transfer the mood, to keep the player in the game...