Ok, I admit it... I'm a dreamer, I run around in this game and I summon up loads of ideas and (at least what I think) cool skill lines for this game. At the moment? Acrobatics! It's from the single titles and I really missed it in the Skyrim addition. So here is how I think it could work here:
Flanking Leap - Vault over the target and get into position behind them, gaining a damage buff in the process.
Flat Footed - Sweep your leg at an enemy, tripping them and lowering their physical resistance.
Hasty Retreat - Perform a backward flip out of danger (potentials for snare morph perhaps)
Agile Defender - Whilst toggled your stamina drains at X amount/rate, during the active use of this ability your roll dodge becomes visually more exciting (flips, cartwheels etc) and you move 50% further. For having the ability on your bar, passively increase stamina by X amount of %.
Who knows, could have passives that reduce fall damage too or something to do with movement speed etc.
If you guys could implement a skill line, or perhaps would like to see one from the single titles, what would it be?