HI DD,
I have a few ideas...first you could do the sashing how you want around each block and just make two quilts?
Or make a row of one of the blocks...add a sashing peice then make the next row the other set of blocks and if need be just add coping strips on the the ends of the shorter rows?
Or you are going have to make sets of blocks and do the math to add coping strips ...but I don't know how to explain that as usually when I do it that way it is kind of a do it as you go and see where it leads you sort of a thing.