Well, if there's a plugin for fearune then see invis has to be clientside. I highly doubt the see SoS stacking is serverside since it seems like more of a bug than anything. Also, if you can see players on your map, do a /who on them and get all that info even when they're anonymous then all that information has to be stored clientside as well. From there how about all the other information pertaining to armor graphics and color? yep.. clientside.
There has to be a way to add this into MQ2Faerune, thats all i was suggesting really. I don't think anyone wants to downgrade to a Fearune item, and then downgrade an augment to a see invis aug, just to see rogues... especially those of us who can turn on a simple plugin to get faerune anyway, now youre downgrading just to see rogues.