So, I got into game and tested new avatar favor system, and here are my findings.
Avatar's Favor is a Pet command, meaning that an avatar needs to be out for it to be used.
Naked, or near naked, Perpetuation cost is about -2 with Avatar's favor up. This makes all avatars near free with the right equipment and without other people's help.
When avatar's favor is up, it is permanent on Summoner, but can be clicked off.
However, the effect is only available if the avatar in question is up. While this does allow avatars to be switched out, there can only be one effect up at any given time.
It takes 30 seconds from summoning for full effect to be in play.
Each avatar has an icon when favor is up that will hit all party members in range.
No idea on how/if avatars are weakened yet. I haven't tested that.
This is awesome!