2. Falcon Is A Very Different Kind of Sidekick Than Bucky
Another reason that The Falcon makes this movie that much better is that he serves as a different kind of side kick to Cap. He's not a childhood friend. There's no role model admiration (or admiration reversal) going on here. Falcon and Cap are fellow soldiers on a mission and that's about it. Sam is also someone who fights very differently to James Barnes. While Bucky gets all 'up in your face' brawling style, Sam goes for more of a "strike and move and strike again" approach. Neither way is better or worse it's a good thing to know that they're so different in what they do. Another important element of all this is how it affects potential for interacting between Falcon and the Winter Soldier. There are some seriously awesome fight scenes on the horizon folks. That's gonna cause some bled over tension for Steve Rogers, because he'll have to weigh his concerns for his best friend against the need to get the mission accomplished. Knowing that the cybernetic powerhouse attacking him is the guy he grew up in Brooklyn with will make things hard enough, but having to get in the middle of that guy fighting his newest partner in fighting crime will ratchet the drama up a few wonderful notches, but hopefully not too many...
2b. Don't have Bucky and Falcon fighting over Cap.
One serious misstep that should be avoided like a public toilet at at a music festival next to a Mexican restaurant is creating an artificial rivalry over who should be at Caps side. While this isn't even something that's likely to come up until after a resolution of the while "mind controlled enemy agent" part of the plot it's still important to make note of. Non-brainwashed Bucky isn't likely to feel jealous at being replaced as Steve's right hand man. Further more, Sam Wilson is incredibly unlikely to give a rats ass whether Steve sticks with him or goes back to running missions with his old buddy. These aren't jealous high school students working out their angst, they're professional freaking soldier/super heroes! Nothing rots a good movie from the inside out like a misplaced romance (think of every
good Adam Sandler comedy and how much better they'd be without the needless love interest) and that also applies to misplaced bromance as well. The primary source of drama in Cap 2 should be "my best friend has been mind wiped by the enemy and I have to fight him". The secondary source of tension should be "this new guy I'm partnered with is kind of a dick". Unless there's a compelling villain or a love interest that fits well in the movie (say Sharon Carter of S.H.I.E.L.D.) there doesn't need to be any drama beyond that.