I'm just repeating what I said in the MCU thread over in the Marvel forums, but I think they should just treat TASM1 & 2 as a vague history for a MCU iteration of Spider-Man, in the event Marvel comes to an agreement with Sony.
Just use those films in a broad way to form a backstory: Peter Parker became Spider-Man, still encountered the Lizard, Electro, Rhino, and the Green Goblin (say it was Norman instead of Harry), and dated Gwen Stacey who is now dead. Also say this all took place over the course of Phase 2. They can pick up with the character now in college.
That said, I don't think CA3 should be the place to bring the character into the MCU.