My current build.
Few notes - I have no idea how useful or how needed Biology for Crossbower, all these exotic poisons - no idea.
Also you need at least 20 effective Chemistry for basic Incendiary Bolts, and better to have 75 effective in endgame.
And you can completely discard Persuasion if you want - you'll get all Chemistry and Biology you need that way.
This build need one more feat - Pack Rathound increases 50 something of carry weight, and I suspect it is greatly needed in endgame where you are on your own supply.
So candidates for replacement - Sharpshooter, or Deadly Snares, or Snipe.
I'll choose Deadly Snares I think.