I have a group of micro electronic engineers capable of producing and assembling multilayer pc boards. Parts are available in catalog, price drops on bulk orders 1-10, 11-50, 50-100... Diagrams for FPGA is mostly open source now, like this one (think it's a bfl single) 800mhash
http://www.ztex.de/usb-fpga-1/usb-fpga-1.15y.e.html or the above mentioned Icarus.
What I have noticed lately, from last autumn, is that no one would like to invest in it. GPUs still make money, and although fpga will not go away anytime soon it looks expensive to build to asics. Not sure if your business case is positive, frankly. Or you have calculated that the Avalons are going to cost more and more in
BTC terms and the others will never make it to the market? In that case, FPGA could realy be the way to go, if asic doesn't become open source.