A very interesting concept in Fatwire is that templates are "typed".
Unfortunately, this is also a concept very easily misunderstood.
The idea is:
For example, you can have News, Articles and Blog posts as content types.
The best way is to decide for a number of common way of render the content: for example: Summary, Detail, Link.
So you can expect to have something like this:
News/Summary News/Detail News/Link Article/Summary Article/Detail Article/Link Blog/Summary Blog/Detail Blog/Link
If you follow those conventions, combining templates becames very easy. You can add in a page a Blog or an Article and then replace with a News.
Just call the template as it should (using a call:template that specify the c and only the Summary - the "relative" way). This way rendering an Article as a summary is the same as rendering a Blog as a summary.
But you start to give different names to template without following any conventions... your code will became a mess.
And you won't exploit the "typed template" approach built-in in Fatwire.