That's a really great find. Like the others said, you really don't want to paint this bike.
For a saddle, a brooks would look great and they're still available. Plus lots of French bikes came with Brooks saddles.
If you live in an area with lots of hills, you may want to play with the gear ratios. That stronglight 93 crank has a 122 bcd which means you can go as low as 37 on the inside. Alternatively, you can turn that crank into a triple but that is a more complicated project.
122 BCD Triplizer, 42 Teeth
Or just go with a 37 tooth inner chainring:
122 BCD Conventional Chainring, 37 Teeth
Kool stop makes brake pads for mafac brakes:
Kool Stop International - High Performance Bicycle Brake Pads Since 1977
Rustoleum is your friend for dealing with the rust on the various bits (like the Mafac brake springs).
Also that water bottle cage is one of the best vintage cages made. It's a steel TA. They're hard to find in decent shape. I know I've looked. So use it. Personally I'd mount that cage on the downtube and the pump on the seattube. The pump on the top tube though is how a lot of French bikes were set up BITD including quite likely this bike:
https://www.bikeboompeugeot.com/Broc...0Page%2017.jpg
If you need inexpensive tubulars, they're available at yellow jersey at 3 for $50
tubular tire sewup tire Servizio Corse $19.95 tubular tires at Yellow Jersey; possibly the Best Value Tubular In America for 2020!
I'd reuse those plugs as they look to be in good shape but replace the tape with black cloth tape like newbaums.
And you will want to overhaul that bike ASAP before riding it. You will need the right puller for that stronglight crank.