Instead of a base template project, we need a modular system for adding dependent packages on a case by case basis similar to python eggs and ruby gems. Just a simple set of command line tools.
Then you could build a central repository of formula scripts for adding frameworks to your project (maybe something simple like how homebrew just uses really simple ruby scripts and built in git awesomeness to keep it up to date and power a good portion of itself and allow others to submit forumlas via pull requests).
The formulas could pull down code from these various project's hosts on an as needed basis and they could be downloaded right into a standard "/vendor/" folder in your project directory when installed. A file would created with install info and time it was pulled so you could easily update the project later with another command.
Then maybe update (or maybe not) update your project file to reference it, add target dependencies, add header search paths or copy file operations for frameworks, etc. (This could be done by generating a base xcconfig file that links in xcconfig files provided by each forumla install into the project).
All these packages could be added to this system and allow the user to search and find great libraries, install them, keep them up to date, and whatever.
(If no body else does this, I may end up do it actually)