With or without the extender, a lens designed for 1/2" will have about a 1.7x crop factor on S-16 film format imagers. As most 1/2" lenses just barely cover 1/2" without an extender, your chances of that lens covering at any focal length without the doubler are fairly poor.
To be on the safe side consider that lens a 14.6 - 204.4mm lens. Which in 35mm (motion picture) is 29.2 - 408.8mm. Keep in mind the Pocket camera has (at minimum) an HD+ res imager. If you are planning to put a lens that never had to work harder than 800 lines of res in front of it (without a doubler), you will be looking at some soft, low con images.
All this being said, I don't think you should consider any lens built for 1/2", if you are going to attempt this for some kind of ENG style convenience, start with 2/3" and a lens designed for HD shooting, and a PROPER adapter (we don't make such a thing, and they are not sold by any ebay only seller). I would also recommend testing a lens before offering up a penny for something on the used market. I know people who have been burned badly purchasing lenses untested from ebay.
However, I'll now attempt to dissuade you (and anyone else) from doing this (ever) without the before mentioned proper adapter. This adapter will require a unique prism inside that will retime the light passing through.
I can tell you that you WILL get image artifacts from any 1/2" or 2/3" ENG lens you put in front of a pocket camera without a proper adapter. These lenses were designed to pass light through a prism which delays the RB photons before hitting each of the 3x sensors in the camera for which the lens was designed. With a single imager (like the Pocket camera) no prism means you get R and B trailing G (not good).
Here's a diagram for those that are having a hard time visualizing what's going on.
For those of you who say...but wait I read about some guy in a forum, or blog, or my cousin told me about some dude who said "it works great". The truth is, anyone who said that doesn't care about the artifacts and that person did those who do give a damn about what they're shooting a real diservice. If you need a good lenses, start looking at some fully manual DSLR lenses, and older S-16mm cinema lenses.
I humbly suggest a Nikon mount Tokina 11-16 with iris adjusting Nikon to MFT adapter, Voigtlander (Leica M and MFT) and Rokinon (any with appropriate adapter) lenses if you need a place to start for new lenses. If you are dead set on a zoom instead of a prime, older manual DSLR lens will probably be less expensive than a S-16mm cine (converted or original) zoom lens. There's many regular 16mm zooms that won't cover on the wide side. No doubt that once the first demo Pocket Cameras hit the street someone will spend an afternoon figuring out which 16mm zooms cover (or at what focal length they start covering).
In the interest of full disclosure, the company I work for does sell both Voigtlander and Rokinon lenses.
Illya Friedman
Hot Rod Cameras
www.hotrodcameras.com