It's very simple, vote with your money. iPad doesn't do what you want, don't buy it and buy something else. Show Apple what's driving people away. They've responded to the bigger screens with iPhone 6 Plus after years of saying they have the perfect size.
Go buy a Surface Pro or Samsung Note 4, they do what you want to do. If Apple releases an iPad or iOS update that does what you want, you can buy it then. There is no point of waiting for something that may never comes.
Millions of people keep buying iPads because it does exactly what they want. Otherwise, they're just wasting their money for no good reasons.
I'm perfectly happy with the iPad's full screen single mode because I use it as a content consumption device, nothing more than that, and it has all the apps that I need and want. If I want more, I'd definitely switch to Galaxy Tablet or Surface Pro without any hesitation.