I have no manufacturing capabilities at home. All custom parts where procured by external workshops. I designed it, so that I can order parts and put everything together at home.

They probably don't have access to a welder and so they can't weld. It looks like they have a router table and a sheet metal bender so that's what they used to make it.

The router table breaks the "no CNC" rule though...

Technically yes however home cnc's that are aluminum capable are so much more common than when I first started back around 2008. Taking inspiration from but not achieving the precision found here: http://oneoceankayaks.com/madvac/madvac_index.htm

While the capabilities have gotten cheaper, the storage space is much more expensive nowadays

I think that would depend a lot on your workshop space, ventilation, available power, and the prevalence of nearby flammable surfaces.