I doubt a single supercap would help you either. They can certainly provide larger currents, but the response time of these isn't that great and might be too slow for the rapid cellular demands (at least for 2G, 3G would be on the border) on connect, so you may need some extra, smaller electrolytic caps to increase response time and all that might again counteract your demands for least self discharge of the whole setup.
BTW, where are you delivering the product to and how?
AFAIK, single LiPos as inbuilt parts of devices get lower risk rating on transport than isolated batteries and/or multiple cells.