Mentor Spirits as Avatars, why bother... Options

[Ophis]

The table for creating a new magic group includes a modifier for using an actual Mentor Spirit as you groups Avatar. This is a fine and good concept to me and I have two magic groups in my current game that have done just this (Dragonslayer and Seductress in case you're wondering). What if any game effect should this have?

I can think of four ideas,

1) Nothing other than kudos.
2) The group gets any bonuses on applicable during group only rituals.
3) All group members get the Mentor Spirit on top of anything they have already (grim potentially)
4) All group members get half the bonuses (ie +1 to stuff) and the full penelty (maybe increasing the threshold for members who already have that Mentor Spirit).

I'm unsure how to handle this but think that it should do something.