Well the Main Problem i have with your theory, that a Logia User must be aware of an attack to doge it through elemental changing, is, that this implies that ANYONE can really hurt a Logia user if the Logia user is just not paying attention and/or didnt see any attack coming. So any good sniper can Kill a Logia User wth a good shot if the User wasnt aware of an attack. But Such thing never happened in One Piece, so i dont believe it.
Also i dont believe that every Logia User automaticly has CoO to doge any attack better.
I beliee, and i have no reason to dont believe it, that the Elemental Form is omnipresent.
But that a Logia User cant Touch anything is something which was never a Role in One piece, dont know why u came up with this.
All that we know is - A Logia User can Touch anything he wants. Like if he is giving a Hand Shake or eating something.
And what we also know is, that every time a Bullet or Sword attack comes to a logia User, it will go through.
The Alabasta example with Smoker is nice. But its like the only time something like this happens, and it goes against all the 'Rules' we learned about Logia in the Whole Plot til that time and from that time on to present day.
Maybe someone needs to ask Oda why Smoker was Pushed away by Luffy insdead of Luffy slipping through. Then we can have a clear answer.
Maybe he would say its the Tension of an upcoming Battle between Smoker and Ace.