I wanted to throw this out there and I know it has been said before.
Why not invest the time in allowing the iPad generate NEMA messages for basic AP control? Make the iFLY EFB a game changer.
To address what I hear as obstacles;
*The iPad GPS is not as accurate as the 740. Leverage a WAAS ADSB-In source or a stand along GPS feed. Or just deal with the GPS accuracy in the iPad.
*The iPad will overheat. I live in FL and fly a tip up RV (Direct sun in a sauna during the summer) and have only once had an iPad overheat because I left it on my seat facing up while I was exploring the beach and I don’t use any case or special covering). Add a fan case or point the air vent at your iPad to keep it cool if your worried. I carry a spare + my iPhone.
*The iPad is not bright enough. It is rarely too bright to read the iPad. When it is I have the same issue reading most of the items on my panel including the 740. Use your hand to shade it if you need to look at something specific or reposition it temporarily.
I would love to hear other obstacles.
Just my .02
Chad