It popped up last night
Shantae: Risky's Revenge got a stealth update on iOS last night that allows for the use of MFi controller add-ons. The game was never impossible to play on a touch screen as it wasn't that difficult, but of course, tactile controls always win out for a precision platformer -- or at least, the option for them does.
I gave it a test run with the Logitech PowerShell and I have to say -- it works like a charm. Everything from pressing the L button to dash to the face button layout mirrored the DS controls. For a few moments, I even forgot I was playing on a mobile device. Great work WayForward! I just hope other developers follow suit.