Interesting project. No updates for 3 years on gba1000?
For mass production you'd need to make cases, replica keyboard+interface, an easy to produce equivalent of all the chips inside an Amiga 1000, re-manufacture 3.5" Amiga compatible FDDs etc so even if that was a PCB layout ready to print out on a suitable machine there is still over a £million in initial investment needed whether you made a souped up faster model or an exact replica of original performance (but using today's production techniques and technologies like FPGA etc).