At the moment you equip an ID it automatically adjusts your reputation to a set template for a given faction.
So for say a Liberty Rogue ID at the moment you mount it all allies will go green (might be adjusted how green), all enemies will go red and reputations of neutrals will remain unadjusted or set to neutral.
Your reputation to any guard faction (even your own) remains unaffected.
That I think is an awesome idea.
1. It does NOT fix your reputation in place, you can only choose to "reset" it by unmounting/mounting or re-buying the id.
2. It can't be abused since it always makes you red to those you should be red to.
RP wise it's like "sirius" got to know you have joined faction x.
Igiss says: Martin, you give them a finger, they bite off your arm.