Ajax Dynamic

I don't know if this is a bit of a foolish plan or not, but I was wondering about the feasibility of creating a framework for allowing modules to relatively easily create Ajax-loadable content.

Basically I envision is a module that creates a new hook (called hook_ajax) for lack of a better name. This module would also include an API for module developers to make the dynamic creation a bit easier (for instance a version of the l() function, but one that modifies the URL to point at our module's MENU_CALLBACK, perhaps with some additional information attached).