The Raspberry Pi and similar tiny computers (I've used Gumstix and Arduino before) are absolutely fantastic for small, experimental projects. But I would not base a flying design on unmodified hardware. The USB connectors used for the two radios, and especially the power connection, are just not designed for long term use in a vibration rich environment like an airplane. It make take some time, perhaps even a handful of years, but those connections *will* eventually fail, probably when you need it most.
But spend just a few more bucks and time with a soldering iron to replace those connectors with something more robust, and maybe a more appropriate antenna, then sure!, it would be a great platform for this use and for so much more.