I don't think you can make generalizations.
Lollers, I should just leave it at that.
It's like house appraisals -- it depends who you get. In the case of guitars with mods, it depends on who ends up buying the guitar. Some appraisers value what you've done to the home, but most of them base it on what everyone else values it at, and that's: size, condition, location. And since you can't guarantee that someone will want a particular upgrade, then I wouldn't do it for the purpose of raising the value of the guitar.