I think the opening frame to the avenger teaser with the boxing gloves serves more of purpose than just cap's been releasing some tension. I think he's been working on his sklls. Mainly the boxing aspect.
I have many(many) gripes with the film but the only one that kept me up at night was the inability to find cap at the crash site of a giant wing the size of a base ball park.
I also thought it was a bit contrived how he became the Army recruitment mascot. Here the goverment just spent untold millions on this super soilder serum, it actually works, people are willing to kill and die for it and then they just dismiss the guy? Why wouldn't they at least send him into battle? You paid for him, you might as well use him. And it would make a lot more sense for the army to hire an actor for these recruitment drives rather than cast this secret government test project, no?
Well they did try and play it off as sending STeve to the "lab" due to his value and ofcourse duplicating the serum. The tour stuff came by way of a business guy I think.