I got the impression he was looking for a purpose for a bike rather than a set of dimensions.
I want something I can ride cross country for an hour, fling round the local woods at silly speeds for another hour and then ride to the cake shop.
there seems to be a fair number of bikes around that allows that and, for me, my Liteville has come closest to delivering my ideal. There are things I’d change though.
I can see of brant can get someone to articulate their ‘ideal’ in a way he can design a bike for and it’s sufficiently popular to justify a small production run to sell to people who have a similar requirement then that’s job done.
It might be a lightweight cargo bike, some sort of xc/playing in the woods uber-bike or the perfect bike packing frame or maybe all of them. Something that takes his fancy and that he can work with someone to design, test and deliver (and sell).
I think it’s an interesting venture and wish him every luck with it.