The obvious solution is to just get 2 devices. Get a 7 or 10 inch tablet for doing document editing, playing games, reading books, and get a 4 inch (or even smaller) phone for quick glances at email, actual phone calls, etc.
There are very few situations I can think of that I could bring a 6 inch phone with me, but that I could not bring a 7 inch (or even 10 inch) tablet and a 4 inch phone. However, there are many situations in my life where I really don't want to have to bring a 6 inch phone, yet still want to have a phone on me. For the price of a 6 inch phone that still doesn't quite cut it as far as tasks like document editing goes, you can get a 4 inch phone which does everything you need in a phone, and a 10 inch tablet that will wipe the floor in productivity related tasks with any smaller device.
That's what I did, I got a 10 inch tablet but dragging the damn thing around with me all the time got tiring. So I got a bag for it only to discover that my 13 inch MacBook fit into the same bag and was only marginally heavier so why bother with a 10 inch tablet? And besides having a 4-5 inch phone, a 10 inch tablet and a laptop is expensive. A 10 inch tablet won't fit into any pocket while the iPad Mini, for example is on the verge of being to large for stuffing into all but the largest pockets and it can't make phone calls. Some of the smaller Samsung tablets can double as phones but I don't like them. I'm going to get an iPhone 6+ phablet that will fit into my pocket and leave the laptop at home when I don't need it. A 6 inch phone is too big and uncomfortable to fit into a trouser pocket but it is still small enough that it will fit into a sweatshirt or coat pocket.