As the primary market of this device is for the open source community the components should be easily obtained and structures easily manufactured. 

Components

Therefore all components should be sourced from reliable suppliers with tested supply chains, examples being RScomponents, Mouser, DigiKey, Element14,  Sparkfun, Adafruit etc. This will increase the cost of the system vs using chinese suppliers such as aliexpress however they are accessible to more people and typically more reliable.

Manufacturing

Most hobbyists now have reliable access to a variety of manufacturing tools.  

3D Printers. Through services such as Ponoko, Shapeways, 3D printing studio.  As well as personal extrusion machines at home and maker spaces around the world. Components printed can be course and take significant fine tuning to ensure accuracy. I am hesitant to use them for high accuracy requirements.

CO2 laser cutter. Less common at home although a staple of hackerspaces. Considerably higher accuracy although they are limited to cutting wood and plastics. Wood components are likely to warp and are also prone to flutuations in temperature and humidity. Plastics are good for components that are subject to wear and need to provide a level of slip. 

Industrial laser cutter. Unavailable as home machines or hacker spaces however they are still easily accessible with laser cutting suppliers in most major citys around the world with cheaper minimum orders available through the years. High tolerance machines that are capable of cutting multiple steel alloys and grades. 

CNC mill & lathe. Harder access to machines, available only to the most equipped hackerspaces and home workshops. Very high tolerance components can be machined in a variety of matterials. Unlike industrial laser cutters commercial machine shops are less likely to do small order runs and therefore the cost of manufacture can be very high.

Material Options

For the easiest mounting and most reliable fit a combination of industrial laser cutting and 3D printing will be used. In this way some users can substitute the metal components for wood or plastics however the design will allow for a higher tolerance fit.

Back mounting frame: Sheet metal

Feeder guidance: 3D printed channel

Feed cover: sheet metal

Take up reels: 3d Printed plastics

All 3D printed parts will come will be designed so they can be manufactured from billet steel in the event someone has access to a mill for fabrication.