While I tend to be an "originalist"...i.e. I want my bikes as original as possible...I am coming to understand having a variety! If the bike is truly collectible in some way/shape/form, then I tend to be originalist. I also tend to be a period correct type person on non-collectibles...i.e. my Tommasini Super Prestige has approximately period correct Campy (that is the other thing...I like culturally correct as well...no Shimano on Italian bikes!).
Other than that...it is more a build as you see fit...I am even coming to see that some of my bikes may need non-period correct.
But...seriously consider it before you make non-reversible changes. Anything that involves cutting braze on's off or etc...please don't...
As for repainting...it is only original paint once...but...there are times/bikes where changing the paint is ok...
So...sum it up...your bike...your way...