A keyboard similar to that of the Surface Book, with an embedded more powerful graphics card (and possibly an additional battery).
A full-size SD slot, instead of a MicroSD, for maximum compatibility.
A magnetically attached power plug, with a small cord and an end being a standard USB-C (just for the power, of course) so you don't have to replace the whole power supply if the cord gets damaged. This, of course, in addition to the already available USB-C for recharging.
Screws to disassemble it without any sort of glue to keep it together, for maximum serviceability.