I like it, particularly like the "things he/she might say".
The presence of high level NPCs might eclipse the PCs though. If Jaddith for example, does nothing in a low level orc attack on the village, then they find out he's megatough in a later adventure, the conversation will go something like this:
PCs: "Hey wait Jaddith, if you're so tough, why didn't you help us in the orc attack?"
Jaddith: "It was not the right time to reveal myself, larger schemes were afoot"
PCs: "People died in that attack bro, you could've killed all those orcs yourself."
Jaddith: "It wasn't the.. um, right time... revealing myself would've only bought greater ruin upon the village uh, yeah..."
PCs: "Dick move bro, dick move."