My biggest concern is the stick/D-pad. The controllers I've tried that use a nub/extension on a D-pad setup have all felt pretty terrible to use in my opinion.
The ability to swap it with a conventional D-pad might be worth consideration.
The shrouds around the buttons and stick-pad worry me a little as well. Depending on the amount of travel that the buttons have (or if a conventional d-pad option is offered), the edge of those shrouds might dig into ones thumb, or present an opportunity for binding.
I'm keeping an eye on this though. I was considering the prospect of building a custom stick with an easily switchable 8-way/4-way gate, but I'd probably be happy with a nice pad option.