I'm not sure how the fonts will work. For example if we get the @ symbol made I assume it can be scaled and then used in the various positions ISO sets use it? Assuming this is the case I would also be up for funding a key
It's not really done on a glyph-by-glyph basis. It's done by keys. The molds are steel or brass (most likely 440C stainless) so they will machine a mold for each key. Key sizes are "fixed" for each profile, and they will generally cut a mold for each row profile 1-4 where appropriate. Every
legend is a single piece of molded plastic. So for US ANSI "3#" key, they'll cut both glyphs into the legend mold. Practically speaking, that means they are not scalable. And for each variation of ISO a new mold is required to manufacture that key in the specified row profile. So your UK ISO "3£" key, you can't just
borrow the 3 from US ANSI "3#" and add the British Pound glyph. You need a new mold. So you might begin to understand why this venture is so complicated and expensive.
Edit: I should clarify - SP might have a typesetting rig they can use for custom legends within their existing font family. For example, the "MASTER ARM" key I designed for Danger Zone might not have required a custom mold if they could make it using their Gorton Modified typeset -- like Gutenberg's "movable type", where they just arrange individual letters to create the legend mold. But that's with an existing font face and doesn't really apply to the Space Extended project.
I also have no idea if such a rig exists for injection molding.