After testing the deck on FNM yesterday, I made severeal changes. The deck played out quite well, won 3 of 5 matches, and it was my first FNM ever in Standard.
Legion Loyalist played out really well, so I put it up to four. I was able to attack almost every first turn.
Spark Trooper was actually better than I thought, rescued me several times due to the lifelink. And playing him while with two battallion creatures already out is REALLY satisfiying :-) That's why I put it up to four also.
I caught me boarding Boros Elite for Soldier of Pantheon multiple times, so I removed Boros Elite entirely.
Although I put in two Chandra's Phoenix as suggested by several people for more speed and aggresiveness. But I had to remove the Frontline Medic for it, they are now sideboard instead. But I think it might work out, becouse the indestructibility seems not that important than making damage quickly, and Chandra's Phoenix is my only card with evasion.
So the whole deck is a bit more aggressive now I think, and more red than white now, with some more burn added. Brave the Elements is only sideboard now. I also added Chained to the Rocks to the sideboard, because I had big trouble with some big Selesnya creatures and a demon in the only matches I have lost.