XF 1.5 how to create custom_thread_view from thread_view

Please people, i need to create a custom_thread_view such that i can choose which of the templates (custom_thread_view or thread_view) my new thread is displayed with.

Such that my thread url will look something different like this www.example.com/custom-threads/my-thread-title.23/

How do i go about achieving this?