Setting aside that I don't have the spare shekels right now to buy a DDS kit... there's simply nothing wrong with the Corsair's PTO. (I have some other issues with the rig, which some contact cleaner and filter resetting ought to fix)
And much as I love the rig, the reality is that it's about 30 years old, and is now the 3rd rig in the shack, so it gets lightly used. Not sure if I'm ready to make the time & $$ investment in upgrading a PTO that's working just as it should.
Now, what would be a neat thing to do would be to (eventually) get my hands on a DDS kit, and build a "new" Remote VFO. That could easily be adapted for other rigs (since the 5 - 5.5 MHz PTO is very common), and would certainly be of interest to those with a Corsair/Corsair II & similar vintage rig that is capable of supporting an external VFO, but simply wasn't purchased with the option.
Eventually, though. I have other priorities in the shack right now, all of which come after getting the house ready to host Little Miss Field Day's graduation party in a little over a month.