If you can run at 10IPM along each axis, would it be feasible to rout large areas with diagonal passes at 14IPM? This is assuming that your speed limit is based on physical limits of the stepper motors, and not on software restrictions. Non-axis-aligned cutting is slightly less precise, as experienced with diagonal and arc cutting in general, but if you are routing a large area in multiple passes anyway then only the precision of the edges matter.
I ask this after watching the demo video for the router contraption.