I would say, do something OnePlus did with their Two phone
Aluminum or Magnesium unibody and then add the swappable style covers
Dark wood, Bamboo, Sandstone (for those who want lots of grip), and a real leather one or two variants.
To make it even cooler, I would follow the the whole build similar to OnePlus phones completely.
1) Extrude and machine metal chassis that will make the edges and maybe partially the back
2) On front side attach a near bezelless screen and you can secure it with glue or crews from inside since you have the back open for assembly
3) Assembling from the back, add MB, SSD, RAM and of course the battery
4) Optional - if your chassis came out not rigid enough, you can add a tension plate on top of components and glue to tie into torsional rigidity of other components. This might mean you will have to go heavy on glue
5) Attach the style cover of customer's choice. Under this cover you can have all of the regulatory stickers, access to memory and sim cards if needed
6) kickstand - use the one similar to the HP tablet where it goes around 1/2 of the perimeter and functions same way as on surface. Make those easy to replace, same like on HP