It might work for a little bit but layout aside, I don't think the board you linked would work very well since it looks like the keys themselves are much bigger than a standard 1u keycap.
Yeah, I'd be stuck with the keys they provide, if I can even rearrange them.
Maybe you can build a smaller ortho for just alphas, but that could also get pricey. :/
True. I haven't seen any cheap orthos, much less large ones. The BFO would work, but it looks crazy expensive to populate. I saw a guy selling a full-size one once, but he had made a custom case and PCB and who knows what all else, and wanted $600 for it. Sure thing, buddy.