One of the best articles I have found until now. It is the use of Nickel Titanium which is a metal alloy with a spring reaction that returns to its origina shape, In other words, if you bend a sheet of this metal, it bounces back and does not deform. This article gives me hope, because it discusses the use of this metal in an ankle orthosis. However, to achieve the results, actions were measured to provide a certain outcome. The more and more I think the best orthotic solution for my case would me a Nickel Titanium foot plate with an extension of the big toe. However the thickness of that sheet would need to be determined in order to bring the spring effect as close to the original toe as possible. Application of the Superelastic NiTi Spring in Ankle Foot Orthosis (AFO) to Create Normal Ankle Joint Behavior

Also an interesting article that refers that Nitinol (Nickel Titanium) is still not that commonly used in orthotics. Nitinol for Prosthetic and Orthotic Applications