Take a look at the newer Thinkpad T series, the T440 and newer are much thinner, lighter weight 14 inch laptops that slot in between the MBP 13" and the MBP 15.

Take a look at the newer Thinkpad T series, the T440 and newer are much thinner, lighter weight 14 inch laptops that slot in between the MBP 13" and the MBP 15.6" in both size and weight. Screen can be upgraded to 1080p and beyond, parts are very well priced, nearly everything is still user serviceable, and you can pick up a T440 for not much. Debian & Arch both have full support for the hardware too!