looking closer, The part roller motor mount could be made in 3 lasered parts.
One flat part from 2mm steel plate, and the bottom as 2 parts lasered and CNC bent with a way to bolt it together.
Part Z motor mount could be water jetted from 10mm aluminum and then finished on a milling machine, although the bolt size would have to be maybe m6 or m5.
Motor mounted with standoff brackets or just longer conduit.
Middle end can be water jetted although the bolt holes I would not water jet, just drill them out. You will get some artifacts on the end holes and the machine time goes up because of the piercings.
Alternately I could water jet delrin or HDPE sheet and machine. Machined Delrin looks like injection molded parts when done.
Same with Middle Joiner. Water jet and a final machining.
To save money I would leave with mill finish or we could powder coat them which adds about a week to the process.
Now if we could figure out how to cast them and use resin…
Corner blocks I would use aluminum bar stock or delrin. Cut to length on a lathe, then drill out on a milling machine. Attach the belts with a electrical connector like I sent in a PM a few days ago. Delrin would be cheapest to machine.