I think for a generic ANSI layout they need to add moulds for 2.25u, 2.75u, and 6.25u if DSA is unsatisfactory for the spacebar. Might be worth their while if it unlocks the ability to sell a lot of key sets.
On the other hand given I am thinking in terms of building a one-off keyboard their capability to produce some sizes you don’t often see intrigues me. According to this 2012 brochure
they can create 2.5u, 3u, 4u and 2×2 caps—I wonder what sort of innovative layout I could concoct with some of these—but, alas! weird sizes have little-to-no chance of being the basis of a successful a group buy.