Well, I wasn't going to change anything on my D'A when I got it, but wanted to try a few things on it, plus I got it used and the guy before me who had it, didn't take care of it. It had oxidised tuners, bridge, stopbar, etc. It kind of freaked me out, cause he didn't mention all that. :S
I upgraded the neck pickup to an SD 59, the sound got really upgraded, warmer tone, a bit more bassy sound, the mids started feeling like they were there. I also changed the cable input to a Switchcraft, the bridge and stopbar, to an ABM bridge and ABM Aluminium tailpiece. Amazing parts, totally recommend them, the guitar got even more sustain.
But the real upgrade I did recently was changing the SD 59, to a Lundgren Heaven 57 with an Aged Nickel cover. Damn, the SD 59 sounded so muddy in comparison to the Lundgren, tighter bass response, more mid range with a nice punch (something that's missing from the Vestax D'As and comes closer to a Gibson ES-335), the highs are there but not piercing, really gentle. To me one of the best PAF style humbuckers out there at the moment. I totally recommend it.
So the final changes will be:
1)The bridge pickup will be replaced to a Lundgren Heaven 57 with Aged Nickel Cover bridge model.
2) All the wiring inside the guitar will be changed to either George L cable or Vintage 2 braided cable.
3) All pots will be changed to CTS 500k pots. (Drilling will have to be made, since pots are not metric)
4) Both Caps to Jensens .022.
5) 3-way switch will also be changed to a Switchcraft short 3 way switch.
6) Pickup Rings will be changed to Madagascar Ebony Rings (for even better tone)
7) Will upgrade the Nut to a Tusq Nut, Graphtech probably. I would go for a bone nut, but there is a case that it might actually provide more volume to one string than the others. At least, that's what my tech says.
8) Last but not least, I will install Tronical Robotic Tuners for easier tuning, plus I am a sucker for whatever gear Kurt uses.
I think, there aren't any other changes to be made on the guitar. Probably a refret when it's going to be needed.