You said in your question

most Earth’s flying animals have beaks because they are lightweight

and yet you want to put a burden on the animal by loading it with a jaw. You are therefore putting your animal on a preferential route for extinction.

More weight means

• more effort to fly
• umbalanced flight
• increased weight due to the structural changes needed to use the jaw (if you want to bite you need proper muscle mass to move the jaws, and more robust skull bones to support the muscles. All of this come at a weight)

and this cost has to be payed in exchange of what? I see no advantages over beak-equipped animals.

You said in your question

most Earth’s flying animals have beaks because they are lightweight

and yet you want to put a burden on the animal by loading it with a jaw. You are therefore putting your animal on a preferential route for extinction.

More weight means

• more effort to fly
• unbalanced flight
• increased weight due to the structural changes needed to use the jaw (if you want to bite you need proper muscle mass to move the jaws, and more robust skull bones to support the muscles. All of this come at a weight)

and this cost has to be payed in exchange of what? I see no advantages over beak-equipped animals.