A rusty bridge on a 'new' Fender Pino stopped me from buying it. Trying it in the shop I asked if the saddles could be raised a bit, the tech tried and said no sorry they're fixed, to which I said - you mean rusted in - he agreed. All the metalwork was too rusted for my liking, unplayable with a very low action so I never got a Pino!
Good advice above from @dyerseve
In the good old days amps couldn't handle the 'massive output' from the pick ups so a resistor was fitted to drop the levels a bit.
I don't see any earth wires soldered to the pot bodies, so no decent grounding there, only the mechanical connection between the pot mountings and the tiny piece of copper tape on the scratchplate. Can't see if the copper is properly earthed either.
Difficult drilling from the split end because the drill will bite/snag. If you take apart and drill from the back it would be better.
EDIT: not sure if the thread in the back would allow a big enough drill to pass through without damage, it's not something I've actually tried!
@dorsetbod My son's g/f's dad has started making leather goods, custom made by hand and doing guitar straps. If you would like to contact him, here's his facebook link;
https://www.facebook.com/sussexhandcraftedleather/
It's a very small - one man and his dog - operation and he's keen to get started, at very competitive prices!
Simple job especialy as you have the hole already, another socket wired in series with the original gives you the 2 outputs, two standard leads for split or one lead in either socket for normal.