I recommend doing it for the same reason I'd recommend changing a classic car with a generator and 6v electrical system to an alternator and 12v electrical system in the course of restoration.
It's much more practical, will not adversely impact performance, and you're already "under the hood" working. I don't think you'd ever regret it. We have a few pairs at our place that the mod has been done to.
I don't think the originality is a major concern with these mics-- even the most valuable microphones are foremost tools that get used (unlike some other musical instruments, whose collectible value can sometimes outstrip their utility value). They will be more useful and practical after the modification.