I'd be intereseted in a couple of boards.
As for layout, ports on the back would be great and things like the sd slot on ribbon would be good to, as long as the board width is less than 5.5" I would be happy, then it could be built into a external disc case like Mavmiga and myself did with his Efika. Here :-
http://bbrv.blogspot.com/2007/07/macmigaefika.htmlGaz
http://www.lincsamiga.org.uk