I think the primary challenge with a pure native code solution is that each library works a slightly different way and not all will make it possible to trap the callback directly.
As these APIs change and evolve, we'll be constantly monitoring them and adjusting server side - as opposed to having to change your mobile client code.
Looking forward, we're also planning to do a lot to help speed up this process and enhance it with other features and services.
Really love the idea though, hope we get to see a purely device based version of this at some point (by chute or somebody else).
To your second point, I should probably clarify. If anyone begins by using Photo Picker+ we will grandfather them in and never charge for that use of the API. In the future there may be other paid components or features of the API that a developer may choose to add, but that will have no bearing on your use of PP+. Thanks a lot.