Last time I looked to buy a new hub (Easier than Mirror Port in some cases for trouble shooting) I had trouble finding even a fast ethernet one. There may be gigabit switches but I would guess the selection is not that good so you might have trouble finding a production quality one. It also sounds like something that might not even work (I'm no electrical engineer by any means, but sounds like maybe heat or "backplane", if a hub even has this notion, problems).
I would first be very sure they know what they are asking. I would find out "why?" because maybe you just need to implement STP or something like that. The general wisdom is to "pick your battles" -- this sounds like one worth picking.