I'd be down for some rejected boards too.

Heck... if the boards just do "adds" rather than hashes, I think folks here would be salivating to put them in their starter kits.
Not sure I follow you j
Would be some expensive placeholders.
I'm wondering if someone will want to design dummy plugs for the slots, so they can space their boards out more. Makes sense to me...
[EDIT] New M-board provides 4 banks of 4 slots. To fill the first four cards, you would place A1, B1, C1 and D1, which are spaced apart, so my comment above might apply more to v1 M's.