Hi Mitch,
Hmmm intersting thought. iApps are to be used to initially create all the objects required for that application. However having said that I know that one can modify the iApp presentation code to ask if he/she would like to use existing pools, monitors, clientssl, caching and compression profiles to name a few. But the big question is can you import an existing virtual server. I think that will be your biggest hurdle. Using get_items /ltm virtual in the presentation code will definitely return a list of known virtual servers for you.
All iApps I've worked on to date are about creating the virtual server initially as well as attaching the relevant objects associated to that virtual server. One would need to test in the lab especially what to use in the implementation code to somehow assign that virtual server to the iApp without having to create it.