As for the general idea of fitting modern components to retro frames.... why not?
I find the whole idea of slavishly sticking to correct chainsets and components, down to the last nut, bolt and fixing utterly bizarre. If I were restoring a significant bike then that's a different matter, I have restored motorcycles and cars in the past, and spent hours hunting out the right switch or light or door panel etc. But in the case of a practical ride-able bicycle, what is the big deal with fitting modern components?
Why bother with old bikes at all? A bike is not just the frame and forks.
52/42 or 53/39 chainsets are for racing not general pootling around. I mean what did people do in the old days before "compact" chainsets if they wanted lower gears? That's right, they fitted touring chainsets with smaller spiders, which many manufacturers offered, even Campagnolo had their Victory and Triomph models. For even lower gears you would have a long cage touring rear mech which could handle bigger sprockets than about 24.