For us if it is "Safe" and "Fly"s Right" it is "Right".
For me too.
I especially don't like warbirds being flown in meetings almost like Pitts, but that's another subject.
"Would you rather I spend maybe $20,000 to make my glossy black accurately marked plane semigloss..."
If I were rich enough to buy me a Mustang and if I would notice at the end of the restoration that the budget is getting thin for the sophisticated finish I had originally choosen, I would simply choose a nice Pacific P-51 scheme, an aircraft left in its glorious natural aluminium finish with for instance a simple colorful green tail, and of course a perfectly done noseart. This way, I would even spare some money and in the same time have a beautiful and accurate P-51 ! Frankly, budget is not an excuse for not choosing the "cool and accurate" option instead of the simple "fun" / "it's my money" variant.
"...I'll save my money for the engine because that will bring me safely home..."
If I would find myself in having to choose restoration options just to be sure to have a safe engine, I would also think to myself it would have been more reasonable to buy this nice T-6 instead of that beautiful P-51.
"... and paintjob B (personalized, lets say)..."
Just curious, why a British guy will never paint his Spit in a "personalized way" ?

"...The historical conneciton to the past is diminished..."
That's right.
If I see this beautifuly newly restored Spit I, that you've all probably seen, I'm back in 1940.
I I see this Mustang more glossy than Paris Hilton's car, I would think : "wow, this dentist looks to be rich, I would go to him if I've trouble with my theeth, he must be good."
"...the flat and semigloss paints might have a useful life that is less than the gloss type..."
I remember a conversation, perhaps here, where someone from the team which painted in England a Yak-9 in a very elegant matte grey said that "matte doesn't mean always more work."