That's a cool idea. Going to file that away for another time. I imagine you'd maybe run your phantom voltage a little higher to overcome the ESD diode drop?
The voltage drop is probably already accounted for in the allowable range unless it's a very low voltage chip. The main concern is you can't get away with anything high current. An SPI flash chip should be ok though, it's only driving one pin and you can choose whatever rate you want.