The production version won't have a dedicated backlight key; see attached pdf.
So who thought it was a good idea to make the big first image on the page be of NOT the product you are making? This campaign is a bit confused I think.
It seems too specialised to me - for general purpose prototyping which is what you are trying to aim at - especially given the LCD segment display.
Really would be much better with either a pixel display, or a good old character LCD, a small-size one you can probably get 4x16 in there, then you can dispense with the co-pro, just have an I2C bus expander.
The pre-printed button labels would annoy me, I don't want my "start" and "stop" buttons labelled "F1" and "F2" etc..
Many moons ago there was a games "console" called a Tunix (in NZ, in the US it's the Emerson Arcadia), it had controllers with a membrane numeric keypad built into it and the games came with printed plastic overlays that clipped into the controller over the keyboard. You might want to consider including some sort of keypad overlay feature into your enclosure - you've gone part the way there with your label insert.