Well if all you're trying to do is run vertical on one cabinet and horizontal on the other, there are plenty of monitor switches out there.. Just set the switch to one side for horizonal and one side for vertical.. As far as the IPAC Splitting goes, I'm really not sure.. As far as I know, Keyboard signals start to degrade on a wire over 6 feet long.. (It may be even less for all I know, I'm not sure), so if they're going to be right next to each other, it might be ok.. The wiring will definitely be interesting, but I don't see why you couldn't do it.. (You may want to pump the wires through some kind of signal amplifier, but I'm not sure exactly what you'd use)l..
Sorry if this reply is kind of vague.. When I'm awake tomorrow (AND SOBER) I might be able to actually point you to some products..
--NipsMG