Simple Cockpit-build  without electronic knowledge:

Because I was  nerved about the continuous fumble of keyboard shortcuts, I've decided to build something  simple to handle and cheep but  useful ,
and as one already known, you can  still connect 2xUSB keyboards to one computer  ....

So then you buy a cheap USB Standard Keyboard (7-12 EUR), and  disassemble the USB-keyboard-controller  from it.  
Then redraw  the  original lines normally (8 contacts) and columns  ( typically 18 contacts ) arrangement of the keyboard,
buy a few meters stranded wire (preferably insulated 0.14 mm ²), a few printed boards, 4 dual-switch (for "SHIFT" "CTRL" "ALT", "ALT GR")
or adjustable capacitive proximity sensors with potential free contact, and a lot of buttons.
A couple of press clamping plates for housing would be good  too.....
You assign the buttons as desired (preferably after SINGLE, SHIFT, CTRL, ALT, ALTGR arrangement),
and put everything together. Film-sheets  on it, finished.
If capacitive sensors should be used , you have to put these very close with those provided  panel portion of the cases,
stick an aluminum foil  under the design foil sheet  and  contact  this with the surface of the sensor.
By the way, would be better if the units are mounted separately to avoid false entries.

Mine will look like this: