I think the field types of K2 should make a branch to 2 versatile efforts: Simplicity and Extensibility. The first branch can be the old implementation of fields in K2, the second should be include JParameters as modell, so coders can integrate their own code. Flexi Content is not as good as K2, but you can implement field types much better.But now I see, K2 uses plugins to integrate code ... good, I have to learn.