It is so annoying that all current smartphones are so large and heavy. The XZ1 Compact could be even smaller now considering the large case frame around the display. That would be amazing.
The phone I am currently using has the following dimensions: 165.2 x 75.7 x 9.1 mm (6.50 x 2.98 x 0.36 in). I think it is a sweet spot for me. I would not go for larger than this.