which design pattern to use, so client can define their own version of that type

I have a interface of IType which has solve() method in it. Their are two concrete class concreteA, concreteB, which implement solve() method. Their is also a TypeFactory which takes care of creating object for concreateA and concreteB respectively. This object creation part is exposed using Facade design pattern to client.

My question is how I can expose functionlity in facade class to let client define their own defination of IType to support creation of UserDefinedType?

I think adapter or decorator pattern can be used, but I am not sure how to expose it through Facade class.