For 1 some quests already do this, the latest quest with the amazing detective did this for one, and several others. I see no reason why all quests would be like this as it makes sense as a storytelling point of view for you to go back to them, imagree some should, some shouldn't but it's already like this.
In game messenger, I also don't get, you have tells for 1 to 1 and have party chat to chat to your party, say to chat to people around you and shout for everyone in an instance.

Moogle mail we are getting in 2.0

Groups that can flag themselves as searching for members, also already in the game, just no one uses it. It was the original way that parties were formed and no one used it. It's still there by the way under the party menu.