I think if you ramp up the allusions that there are other/many heroes out there aside from the Avengers in AOU, you could drop Spidey in there with an after credits scene, then maybe have him Civil War.

Of course he wouldn't have a major role. I think the MCU heads will wait until they get to do their own Spidey movie before he gets featured in a major way.

EDIT:

Come to think about it, I think a good way to go about it would be to use plot point in the comics from the 80's/90's where Spidey was a reserve Avenger. Maybe after Ultron fucks shit up, Shield/Stark/Fury decide that they need more personnel and/or firepower and should groom replacements/stand-ins for emergencies. Then you see Spidey and perhaps Ant-Man in post-credits scene....
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