Teensy is not needed and there is no reason to use it when SMD controller can be done at the PCB fab. I would rather spend some extra for factory SMD component assembly. It definitely makes for a much cleaner design and it's easier for most end builders to complete too when all that needs finishing is adding the choice of switch.
To be serious, we are rather far behind in offering complete package. Sure we have some nice PCBs under us, and a few case, but nothing has been designed all together, to be offered as a complete yet here. By this I mean you can buy ALL components from 1 groupbuy if one wishes.
I was actually thinking of kicking off something, with some help from some people to work together on something cohesive from the beginning, PCB, casebody and GMK keycap to be offered all together for MX based updated 21st century version of AT layout. Keep layouts to most common, ANSI, ISO, JIS variants. Make 2 version of same case design, one cheap version made from acrylic, POM or something, and deluxe version from aluminum.