Also, i dont believe it to be interesting to reinvent the wheel. Raspberry Pi is a perfectly cheap solution for running CGminer from out of. It will be much more expensive to have this on each and every board..
Ethernet mac chip for pic32mx7xx cost ~0.99$ (in reel), rj45 socket less 0.5$, some xtal, res, caps etc and ~2cm² PCB area. Say total max 4$. RJ45 socket can leave unpopulated so customer can solder it if need. Other parts pnp machine lay board <0.1s.
One board can act master and chain other 16.
I see raspi ~50$ vs. ~4$ (plus onetime code/firmware generation = port cgminer to mips and some micro tcp stack).
If burning boards are done say 2000pcs and every 16 needs raspi -> 125 x 45$=5600$. I can't say is it enough to modify board now. Atleast it reduce one board + wires when suitable firmware are done.
I see it good option, not reinvent wheel.