I stumbled upon an interesting feat called Draconic Breath in the Complete Arcane and decided to read up on it. It reads as follows:
You can convert your arcane spells into a breath weapon.
As a standard action, you can change arcane spell energy into a breath weapon of your draconic heritage energy type. The breath weapon is a 30-foot cone (fire or cold) or a 60-foot line (acid or electricity) that deals 2d6 points of damage per level of the spell that you expended to create the effect. Any creature in the area can make a Reflex save (DC 10 + level of the spell used + your Cha modifier) for half damage. This is a supernatural ability.
There are plenty of spells available, which empower breath weapons that are not racial or class features such as Stunning Breath applying specifically to the Dragon Breath spell. However, I wonder if a PC, simply by virtue of having the feat above, qualifies for Metabreath feats (which is apparently not the case, according to a thread on the Draginfire Adepts's breath weapon in a similar context), and/or feats that apply to supernatural abilities such as Widen Supernatural Ability, since the feat in itself does not grant a supernatural ability. Or does it?
The feat Draconic Breath doesn't meet the metabreath feats' type requirements
The feat Draconic Breath (Races of the Dragon 102) doesn't grant a breath weapon "whose time between breaths is expressed in rounds" (Draconomicon 66). The feat Draconic Breath's breath weapon can't be affected by metabreath feats.
The feat Draconic Breath grants a supernatural ability; feats that apply to supernatural abilities can be used with it...
Thus a character could pick the feats Empower Supernatural Ability (Tome of Magic 74), Enlarge Supernatural Ability (Tome of Magic 73), and Widen Supernatural Ability (Tome of Magic 75) and apply their effects to the feat Draconic Breath's breath weapon. (The feat Extend Supernatural Ability (Tome of Magic 73-4) won't do anything.) No further metamagical supernatural ability feats were officially published.
...And so can breath channeling feats
Breath channeling feats (Races of the Dragon 101) don't have the restrictions that metabreath feats have, requiring only a breath weapon. Use those with the feat Draconic Breath's breath weapon; I recommend the feat Entangling Exhalation (Races of the Dragon 101).