Great suggestion, @Bastien_Siebman!
I think often times clients and coworkers struggle with the idea of having multiple projects for one given initiative (master project). If there was an ability to add to an existing project (like you can with import via CSV) then I think having templates for stages of a project would be a fantastic solution. I would even recommend that one of the final tasks of the previous stage would be to create the next stage using the appropriate template!
Maybe there is an external tool that achieves this or I’m mistaken in my understanding that you can only use templates to CREATE projects and not add to them. Either way, great tip! 
