16' Tall Load Bearing Wall
Yes. This is called balloon framing: https://en.wikipedia.org/wiki/Framing_(construction)#Balloon_framing

The catch in 2015 is that it might not be all that easy to find 16' 2x4s that are all that straight. 

I'd personally go with 2x6's in this case for added rigidity, load bearing abilities, increased insulation space (important on that high wall) and just plain easier to deal with in terms of getting straighter walls. 

Unsolicited suggestions:


have you considered leaving the gap along the side wall? That will allow you the maximum head space up in the loft area towards the front (tall) wall.
I'd consider going with a 3' gap rather than 2' just to make it that much easier to get stuff up into the loft (namely furniture).