The way I look at it, any bike can be an all-season rider or tourer, it's just what components it may need to do so, like fenders, racks, gearing, etc. If it's already in perfect condition, I'd think there's no good reason to paint it. Take that money for buying some suitable tires, cables, brake pads, chain and the like and getting it back into working order.

Very few of the bikes I've owned were Reynolds frames, or any high-end tubing. What makes the high-end tubing more desirable is that you get good strength with less weight, something more desirable for racing bikes and not necessarily for touring or city bikes. The lesser-material frames aren't less functional or less strong, they're just heavier. That Peugeot steel is a fine material, it's been used for ages on millions of bikes. It'll last longer than you will, I bet.

Vintage? I don't know. My bikes are all from the '70's, so vintage to me, is a bit older.