To each his own as they say but here's my .02 worth...
I too am very much a purist when it comes to restorations. Yes, some mods seem to make sense and make a vehicle more "drivable" but something to consider is the fact that they were designed to be "drivable" in the first place.
Perhaps not in the way the modern world considers it to be, but drivable nonetheless.
When there vehicles were engineered I believe that they used the best combinations know at the time to come up with the designs that they did. Things like brakes and suspension were carefully calculated to work together with the drivetrain of the day. Truthfully, I reason that CMPs were made to go a certain speed for a reason. Messing with that by adding "performance improvements" only works as a total system- that system is only as strong as its weakest link. If one were to start increasing HP, speed etc it would only be reasonable that things like steering, suspension and braking should be improved upon as well... Vehicle engineering is in fact a total formula afterall.