Hey @moxierichard, have you looked into Cameras, Mesh Collisions and Gravity - Babylon.js Documentation (defining an ellipsoid for your character mesh and using moveWithCollisions)?
Could you check out the Playground from this Question post: Raycast to check if player is standing on ground? It uses WASD for movement and SPACE for jump and utilizes moveWithCollisions and raycasts to check if the character is on a floor.
Edit: Added a slide for you 
https://www.babylonjs-playground.com/#3EDS3A#16
Also, I don’t remember what was in the Espilit soure code, however it makes sense that raycasts weren’t used, since there was no need to check if the player was on a ground (e.g. for jumping logic). They would only need to use moveWithCollisions.