I think you're overthinking this fellers. Neco and Cane creek are low stacks anyway. So two washers 3 or 4mm thick should do.
@Woz - Would you be so kind to do a wee search on French ebay for French BB taps? 35 x 1. In case there's anything reasonable. My attempt via ebay.co.uk only returns a couple US listings.
@Mickeyspinn how bad do you think stainless will be to tap on a scale of 1 to 10? I don't have a 24mm bit to drill out alloy, and my woodworking machinery is way too inaccurate for the job anyway.
I'd rather avoid the need for custom machined parts if I'm looking for a workaround that simplifies things for everyone. And I might need some machining help in the nearest future anyway