I'd like to see a little more info on the change you propose, even if not everyone would want to use it I think it's likely reasonable to put into the acs-templating package. The template search path option in particular sounds like it is generally useful.
As far as custom for widgets and the like - yes, additional small packages make sense. I keep thinking I'll find time to clean up (generalize) the Greenpeace widgets and add them as a package to contrib. This is a perfect example of something that belongs in contrib, not in acs-templating, because they require Javascript to work and heavy dependence on JavaScript is not something we want to put into the toolkit proper. But they're useful in a controlled environment (in GP they only appear on staff pages and GP controls which browsers are available to Planet staffers so complex Javascript's OK)
