Fair enough regarding mundane detection. Assuming you escape from Wyld Hunt leader and his cronies, only to bump into him waiting in the check-out line of the Nexus Wal*Mart, the artifact will continue to mask you so he doesn't challenge you to a duel in the middle of tobacco and impluse item rack.
Avoiding Sidereal machinations is a bit trickier, but only slightly. Sidereals are really good at finding and manipulating events surrounding young exalts because the target's essense is low. As your essence increases, it becomes more difficult for them to manipulate things around you. People of strong essence carve their own destiny. So the artifact would increase the difficulty on their Craft (Fate) roll to manipulate you and events around you, just as higher essence would; but, unlike high essence, it won't show up on the Loom as someone rewriting their own destiny. Sound good?
Regarding the number of players, I won't make a final decision on this right now. That'll wait until saturday (I will be around, but I imagine we'll end up finalizing characters and introducing the mechanics of the system to new players rather than diving right away into the actual story). Having the group split along various niches is not always a bad thing (though it can led to disfunctional rifting if improperly managed). Once I had a circle that had a common goal: leading a rebellion in Harborhead and liberating that nation from the Realm. We had a mix of approaches as far as acheiving that end. Some of us spent time training the local tribes; others spent time trying to get the tribes to put aside their differences and unite; others worked the social angle and encouraged the local provincial government to take an more active role; others turned to the gods (particularly the gods of war to help get their favor in the coming war); my twilight secured a five dot manse to serve as our base of operations and began mass producing supernatural weapons. Everyone had their own style, their own minor goal, but it worked out pretty well when put all together.
On the flip side, we once had a character who was obsessed with discovering her past. She was sort of a Wolverine-type character: someone had done all sorts of experiments on her, which had caused her exaltation, but her memories of those experiments had been wiped. She worked well with the group at first, until she had enough information to pursue her past directly, then she set off on her own because her goals no longer matched with the rest of the circle. That was pretty much the end of the character in that game, unfortunately. Stuff like that we'll need to avoid and I've already discussed this issue with some players.
Clayton