Mimaki does use Epson heads, though I believe they use two seperate heads - one for discharge and one for colors. I would not recommend it as the discharge inks are not good for the heads and require washing of the garment prior to wearing. In the incestuous digital world that we live in, if it works (and is viable and not patented), it will be copied. Notice that no one else is using a discharge system.
JMHO
JMHO