I think you are worrying about something called obsolescence which we can do very little about.
Even if you go the route of mach3 etc you could still be left with motors and drivers that will eventually change hopefully into something better.
My own take on the subject is that in a working environment I would go for a dedicated controller system have alook at the http://www.eaziform.co.uk/ systems they can use drivers from a variety of sources or they make their own drivers.
No doubt you caould use a mach3 system as many have done but I have my doubts about using a pc in a factory environment.
I know from personal experience that a PC in a factory environment will suffer from some unusual mains variations which cause alsorts of problems.
I wish you well but I suspect you reaching for the moon!

Peter