Does it make sense to feed the ioni with a signal meant
for a stepper and let it drive a Brushed DC?
It can be set up so that pulse rate is just another way to send a velocity command, with the position loop inside LinuxCNC, or you can put the position loop in LinuxCNC.
Just about any way that the Ioni can work can be used by LinuxCNC, but their SimpleMotion protocol is probably the most difficult to integrate with LinuxCNC.