This!
I have used a few DAWs and synths on IOS, and others allow you to learn control ids to map to instrument controls, so it can be done!
Even if it were just the transport controls that would be a huge bonus, once I am on my keyboard, I would rather not have to keep leaning over to touch the screen of the iPad, pulling on cables and generally putting my kit at risk…
It seems this is a very popular request, and has been for over 2 years - are you even looking at this topic?
Nick.