The older a bike the more inclined I am to leave it mostly old. It depends is mostly my attitude these days. I prefer the look of a bit of patina on things.
There's some that would have repainted this bike:

I'm not sure if it's a PX-10 or not but it's some nice French bike and it cleaned up amazingly well. I love the look of the worn paint and the components have all been cleaned up and polished so it looks cared for.
I powdercoated a miyata 1000 that I picked up, but it was totally ruined with a few horrible paint jobs. The local powdercoat guy did an amazing job on it and I use for touring and randonneuring so I appreciate the durability of the PC.

I use the miyata a lot, hopefully this will see another 5,000km this year. I could have done a better job with the decals/stickers but they are common enough that I can reapply them in a few years when I wear them all off.
Personally I don't worry about the value of these bikes, both are more valuable now should I want to sell them but I enjoy them and use them so resale isn't a real concern for me, nor are they historically significant in any way.