I disagree - we often saw the negative impact of what happens when people who were originally involved in the process are calling the shots on a restoration or a new master - most obviously of course George Lucas, but then you have all the new restorations of James Cameron films Like Terminator, Aliens or Titanic, supervised by Cameron getting a teal and orange look, same goes for the Blade Runner Final Cut, LOTR FOTR EE BD, Matrix and others - the best way in my opinion, is to have it done by a competent expert colorist, who knows the processes that were involved at the time of the movie's making and is able to replicate them. And you say:

"someone who had nothing to do with the film (i.e. what people refer to as "professional") subjectively decide the tone"

to which I would counter, that such an expert, unlike someone who did have something to do with the film, is actually far more likely to decide things objectively.

And worn out film stock, if it's non-fading, like the I.B. Technicolor, is definitely a better source of information, than somebody's memories of something that happened 30 years ago - memories get distorted in unbelievable ways.