each daughter board will handle 2 thermocouples I personally would convert the Bed to a know Thermistor such as http://www.ebay.co.uk/itm/Modular-Screw-on-M3-Stud-Metal-Thermistor-for-Reprap-Prusa-3D-Printer-Hot-End-/221892120007?hash=item33a9cd0dc7 or one of E3D';s semitec 104 thermistors there are lots of options there and stick with the Hotend Thermocouples
Yeah - I';m trying not to convert the entire machine to 24v with all that might entail. That may come about in due time but not just yet awhile Tonight I shall mostly be bending my brain working out the Thermistor Table requirements for the heat bed. Of course Repetier does it slightly different to Marlin ... Deep joy, many fun.