We have a lot of Templates that contain many subsets of the same exact tasks. It's very brittle and time consuming when we change the way we do one of those subsets of tasks, because now it has to be changed in more than one place (sometimes a lot more).
It would be less brittle, if instead you could make smaller templates, and embed/link those in other templates (having parent templates). If you change a linked template, it then updates it in every parent template that contains it. There could be an option to unlink it (in a parent template). The parent template would override any project / form values that conflict.
Some of us currently do use smaller sub templates, and when creating a project use 'attach template' over and over to bring in the sub-templates - this gets annoying though and requires re-arranging tasks and so many of our project managers create forked templates with those items already included. A linked/child/referenced template within a larger template would be much easier to work with.