Personally, I think that I would almost prefer to have a well made repro crossguard installed and just keep the mutilated one, but some collectors think that even the smallest original part should be saved if possible. It might be something that can never be definitively proven for sure, but I think your theory is about as close as a person is going to come on this one, Rob! Good thinking!
"Much that once was, is lost. For none now live who remember it."