It will be cheaper to change the controller to the IP-A version, changing the motors and drivers will cost more than the new controller and will also need mechanical changes to the motor mounting flanges. After this you would then need to add a motion controller, because a standard breakout board will not handle the 24V I/O let alone the amount of I/O you will need.
This conversion will take time and this will cost more than the parts if you are paying someone else to retrofit it. Do you have the documentation on the machine? like the wiring or at least the installation manual for the controller and drivers?
before you go any further, you need to know if the existing motors and drivers are actually working? and you need to check if the encoders are incremental or absolute. If they are dodgy or absolute encoders, then changing the motors and drivers may be the way forward, but also changing the controller to an IP-S or M, but i would favour the S version.
I could do it, but i have about four other machines that i need to do first.