My sewing table is against the window because I need the light, but it is pulled back enough that I can place the bulk of the quilt in front of me.
The larger surface you have to sew, the better. If he makes it large enough, you can use the other end for your cutting table. If I had my druthers, I would have about an 8 foot square table, with my machine recessed on one end. Then I would finally have enough sewing room!