Maybe 4 dual purpose slots (so that you can have any combination, from 1 sim and 3 micro sd to 4 sim) would be the Holy Grail
Again, Win/Linux/Android triple boot would be the Holy Grail
Better make it 128/256
Definitely 5.5" minimum, over 6" better
Oh, please no, better use a nice trifold bluetoth keyboard instead!
I would say 5000mAh minimum
... and please think of a 2/3 or an 1" sensor for the camera and a decent, fast, 30mm equiv. lens (alternatively a 3x zoom, if you use a smaller sensor or dual camera, one with a 30mm equiv. and one with a 90mm equiv. lens)!
I dare say hi-fi reproduction is even more important!
what about dual usb-c (one of them tb3, if it makes sense at all in terms of speed) + standard audio jack. Sennheiser, Klipsch, Schure, B&W, Etymotic, etc are nowhere near adopting USB-C for their earphones.