Extendable Raspberry Pi (B+) case with various extensions

This is an extendable Raspberry Pi (B+,2,3) case with a GoPro Mount, which has room for:

* All Raspberry Pi connectors accessible
* A power switch
* A display on top. (e.g. the small OLED Display)
* 4 Mini-DIN connectors serving 1-wire, i2C and SPI connections to external sensors
* 12V input connector to be fed via 12V supplies
* A 12V --> 5.1V stepdown converter
* A 3.3V 5V level shifter for SPI / I2C
* a little ADC board


The design phase is not yet complete, but if you have suggestions, please comment.

There are following options for the cover:
A) No holes at all,
B) Use an OLED Display.
C) e.g. use a 2x16 LCD Display instead of the OLED (from here: https://www.thingiverse.com/thing:2831020)
D) use 84x48 pixel LCD display (from here: https://www.thingiverse.com/thing:2857443
E) a 40mm Fan connection (inside)
F) a 40mm Fan connection (inside)

Also extensions can be inserted by inserts between the corpus and the cover. So the case can be extended vertical