They could've fleshed out Sharon A LOT more all with still letting ScarJo have the large role she did in TWS.
Here's how they should've done it, IMO...
TFA
- Sharon could've been the agent at the end who was trying to convince Steve he was still in the past
Avengers
She could've played a role in SHIELD and been in a few scenes
TWS
She should've been a known SHIELD agent, still assigned to protect Steve but not in disguise as a Nurse. Have her keep her scenes defending Cap at the end of the film. She could've taken Maria Hill's role in the film also and rescue Widow, Cap and Falcon and work with them at the end.
Avengers 2
Party scene, she could've been Steve's date
Civil War
Establish a relationship with Cap and take place in at least a battle.
Oh well though...