I've been using Skype on the iPad as my only phone since the ipad 2 came out. When the iPad mini came out, I tried that and found it to be perfect, in being the largest device that still fits in a pocket, a back pants pocket, or jacket pocket, and can be operated with one hand. A full size or large iPad Pro is prohibitively large to carry around when you're working out between the shop & the office, or constantly going between the garden & the garage or the car or the boat & the hardware store, whereas, the mini tucks in your back pocket, freeing you to carry things that require both hands, can be pulled out and operated with one hand reaching all the keyboard keys, but is still big enough that going back to anything smaller seems ridiculously squinty. The mini's speakers are loud enough to hear clearly at an audible volume from your pocket, so you can actually listen to podcasts and audiobooks uninterrupted while working around the house, without headphones. And of course with a pogo stylus you can take notes and sketch ideas about as well as a pro with an Apple Pencil, only you never have batteries and syncing to worry about.
Bonus, is that a dedicated phone number through skype, and service, runs you about $3/mo. Data is whatever cell plan you use, though it's been months since Ive even used more than T-mobiles free 200mb of cellular allotment, due to the prevalence of wifi. The result is an extra hundred dollars a month I'm not throwing away, while receiving the same functional service. Do you want a hundred dollar a month raise for doing the same work? Same thing.
Only note of caution, I'd snatch up an old stock iPad mini running ios10, as ios11 runs like absolute crap on the mini, and 11 kills multitasking on the smaller display. 10 allows you fast access to calc & notability, etc
Yes it's entirely possible. It's most convenient, functional, productive configuration of a device I've found after trying everything. Given Apples track record with products on the extreme end of usefulness, they'll probably kill it in order to sell you two devices that each do half as much.