Spiderman is not gonna get a movie in 2017 unless it is stipulated in the negotiation. MCU has THREE movie out that year. Unless they are scrapping one of them, just no... I'd be shocked if the rights were bought outright and Marvel reboots three years after ASM2. That's not their game.
Do some Civil War reshoots (where are we with filming that by the way? Did they already start?). Give Spidey a cameo or a small role. Give him a bigger role in Avengers Infinity War. To make room for Spidey, you can take one of the Avengers out of commission for a while depending on what happens with AoU and Civil War, to make screen time for Spidey. Solo Spidey film in 2020/2021 for PIV.
A Spider-Man film releasing last year didn't hurt the three Disney produced Marvel adaptations rekeased. Look at it this way: Disney doesn't have a major film releasing in April 2017. If Spidey releases then, they benefit from that film, and it's out of most theaters by the time they're own big film is out.

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