Have you thought about an API for the XMega event system ? There seems to be a large number of ways peripherals can be hooked together. Both events and events + data. Sort of of a massive cross-point switch. Which may make it complex to program without some kind of tool. Whoever at Atmel designed the event system must have had something in mind. Time to read the XMega app notes more closely.
I'll look forward to your first release. Thanks for your significant effort.