Whats Your goal ?

Unless You have a goal, there is no possible way to procede intelligently.

Itīs unlikely, but possible you could get the old control sw to run faster/better with newer motion hw.
This would mean new motors, aka ac servos, acting as better steppers ( or a new control board at 10x better but forgetting the old sw/hw totally).

It is possible, not difficult, to replace an old industrial control with a new one.
The vast majority of refits are:
-done on simple machines like wood routers
-donīt use or implement industrial standards or safety protocols
-not very well done in terms of io or safety or homing or lots of stuff

The so-called controller is a sw/hw package that determines what and how stuff runs.
Linuxcnc with mesa cards,
machx with cslabs hw or other hw,
or chinese integrated sw/hw are 3 common different paths.
Each has +/-.

To really re-build a commercial machine or equivalent requires lots of io, with some logic.
This is very laborious, and somewhat expensive.
Expect 2500$ in bits and parts, and at least 400 work hours, and at least 200 - 300 IOs.
And 1000-3000$ in the controller, depending.

But...
For 1000$ total lots of people have a home-brew kit running with a basic chinese controller.
With limited homing, squaring, probing, offsets, etc. but it moves. Somewhat.

You asked about a "refit or commercial" and like 98% of people will probably think it is too expensive.
Fine.