Thanks for this opinion of yours, Decio. Although I do think tablets (like Wacoms or similar) work very well on desktop computers – I tend to think you are right.
We are doing Animation Paper for the iPad Pro with Pencil. We have been planning this all a long. Both the iPad and the desktop versions have most of their code base shared. This means 2 things: 1. We will be able to finish the iPad version fairly quickly after we finish the desktop version. The main task is to redesign the interface for touch purposes. And 2. the two versions will be fully compatible. Project files made on the desktop will load perfectly on the iPad and vice versa.
I think Animation Paper will be amazing on the iPad Pro!