I think the thing you need to keep in mind, with Avatar, unless you are building a VERY alternative universe( as I do). Is that you want to focus on the powers they come in a bout two shades:
Blast, Surround, Entrap, but have kind as someone else '1 off powers', or subset powers:
Healing for Water benders- who can Blood Bend (whether its a bloodline, or a particular subset both series aren't clear: Katara LEARNED to do it, but in Korra its covered as it seemes to be somewhat genetic (atleast being able to do it at will without the full moon).
Lighting Bending for Fire Benders... seems to be more practice.. and ability to convert.
But Earth Benders have two subset : Lava & Metal, both of which seem to have a kind of 'talent' component.
Airbenders- Seem to get sprituality/awarenes. ( Aaang 's energy bending seems to be a Gift from the Lion Turtle, and we've never actually seen Korra do it, though she should know how- because she was Aang's life at somepoint.
Now Chi-Blocking that seems to be another thing all together... It seems to be more skill than an ability, so maybe a Talent."