Single pass printers tend to use industrial heads like the Toshiba CE4 (Mimaki's UJF3042/6042 MKII use them), 4 channels would be good, 8 ideal for white base coat, but all depends on materials. Never got anywhere with Epson, so no good deal on their heads. One of the Chinese companies that makes driver boards/kits for the i3200 stuff even sent all their firmware over, so hoping to have some of their boards coming in soon.
Seems lots of printers running over 2 heads uses a fiber connection for raw data streaming to the head and peeking at the firmware, it's pretty much straight streamed firing information. Might try and see if it's standardized to some degree and peek at the packets on the Mimaki and the aftermarket stuff to see if they're talking the same, or similar languages.
Heads are something that will always have to be sourced. Hoping to make open/custom driver and control boards. That said, when going to lots of heads, current handling can get pretty fun. Larger printers also need some mondo motor driving current. Playing with a JFX500 and that mofo has 3 stacked 36V 1KW PSUs packed into it.