The research and design of a ultimaker gantry style printer that has dual direct drive extruder on the gantry is not practical and therefore a new motion platform must be reevaluated. From my own experience the P3STEEL has been incredibly reliable in comparison to other printer designs and i am insure why i had overlooked this. Possible one factor is that the printer bed move in the y direction. I have done some investigation in to this and it seems it has relatively little effect on the print even when the print is high. This was a concern and why i had wnet down a different root. The reason the P3STEEL or prusa i3 variant is reliable is because of their simplicity. Simply the bed moves in the y axis and the extruder moves in the x-axis. The extruder also moves in the z, but relatively slowly. This reduces complexity and is more mechanically rigid.
Diagram shows a typical layout of prusa i3/ P3STEEL gantry and will hopefully be correct route to take.