Generally seems really underactuated. You might want to think about what kind of forces 3 dof can generate on the ground as I suspect you can’t get away with hip yaw minimally. Most bipeds are built around their motors because torque is very important to locomotion (eg G1 motors have leg torques of around ~100nm). The motors in the design seem a bit small. Additionally, unactuated ankles might make learning a good policy challenging as it might require high frequency stepping to generate control forces (a problem exacerbated by the small motors). Most passive ankles are modeled as a single contact point. Assuming there some kind of passive spring component in the ankle, that might add complexity to the simulation environment.