Like others, I prefer to keep upgrades relatively period-correct, though upgrades to more modern components can be done responsibly. Anything safety related, I'd recommend. I also tend to stay culturally "correct," though that doesn't mean as much on a Trek, perhaps. I shy away from spreading the rear dropouts but to each their own - it would open up some possibility to you. Someone once recommended I go aero (brake-wise) on a new build, and afterward, I felt the old non-aero Mafacs worked a lot better. Sometimes it takes experiencing both to realize what you want or need. Same with saddles, give me an old one before any new Specialized...

There are a lot of fantastic new bikes out there. Soma makes great bikes. However, 531 steel isn't all that common despite so many of us on C&V that own such bikes. It's still better than the majority of bicycle frames out there, its a fact.