As to the notion that a larger iPhone is a viable substitute for the iPad Mini...
The Mini's screen is about 2 1/3 times larger than that of the iPhone 7 Plus!
It's THREE TIMES the size of the iPhone 7!
Anyone who thinks that they provide the same experience either hasn't owned or used both at the same time, isn't very discriminating, or holds their iPhone up to their eyeballs!
Likewise, anyone who thinks that the regular iPad can replace the Mini must not curl up with their iPad, read books in a cozy nook, schlep it around, put it in their coat pocket, take photographs with it, do astronomy or stargazing with it, birdwatch with it, go on hikes with it, etc. The convenience factor, light weight, and manageability of the Mini are incredible compared to the regular iPad.
Letter to Tim: Give us an iPhone SE 2 and an iPad Mini 5 and watch pent-up demand and sales soar!