I think a ideal size of skills be max upto 150 mm in length like Nokia 6.1plus.
There are a lots and lots of people who like compact phones. That's why they choose apple. And I'm one of them.
I think upcoming Nokia x7 or 7.1 plus should be as compact as it's siblings 6.1plus and 5.1plus. I bought 6.1 plus for my sister and really liked it's compactness. And waiting for 7.1 plus to arrive in compactness to buy one myself.