Nice story and I get the mentality for sure, as the world throws far too much away.
But, in this instance I’m struggling to imagine it being that good for a bike shop. By the time you’ve searched about, engineered the bits, painted and tested, you’ll have to charge £40 to £50 for time and overheads – without the security of a ‘proper’ factory component being sold to the customer for a safety critical part of the bike.
In this instance I think I’d be selling them a Maxle Ultimate, which are available and better anyway.
I get it for individuals and have done similar things myself with the mountain of just in case ‘spares’ that accumulate over the years but, unless it’s your business and you’re happy with costs, customers by and large won’t pay the right money for such a job on a part that can be replaced correctly.