I was wondering if there was a full keyboard replacement for the CS1X instead of the individual keys, looking at the cost of replacing the keys as opposed to replacing the full keyboard itself is just too inconvenient, does anyone know anything about this?
Mike 
I own the same synth (more like a rompler as they call it) and gave it a little implant operation very recently. You can see how it looks in one of my tweets.
Looking inside, the keys were actually assembled exactly in pieces as sold here on Syntaur, so I am assuming that there is no “whole key kit” unless what you are asking for is some discount on the kit for all 61 keys.
You will see in my tweet that It is possible to replace keys that are actually damaged, but then you will most likely face the issue of yellow-ish keys that have aged over the years.
Although I have not yet tried on my CS1x but there is a method to bring back the original whiteness to a certain degree called “Retr0bright”. I am now testing the method on my CBX-K3 MIDI Controller and so far the method is giving me some breathtaking results.
I hope this was helpful.