That actually could be an awesome idea! It would be magnificent, and a pretty cool/well thought way to introduce my man Spidey to the MCU.
Unfortunately, that would never happen.
First, because of Mark Millar announcement that you (William Cloud in his article.) put in the edit, and because I'm sadly convince that Marvel/Disney wants a young Spider-man to simply acquire the love of the youth, the smaller kids.
"Scenaristicaly" speaking, this is bad.
A young Spider-man does not allow you to exploit all the amount of greatness, emotions, mature content you can achive with more than 50 years of Spider-man adventures to choose stories from to build movies on.
(Not sure if that is quite english...)
And when I say "mature content", I do not mean sex, but serious plot with more dramatic, serious scene.
I hated that Peter returns as Spider-man at the end of TASM 2 with the kid standing in the street. Gwen wa-- IS the love of his life and he should be mourning her more than 2 minutes in the movie. He should have return late in TASM 3. But hey! I'm no writer. (Yet. xP)
Still, a Civil War is no place to a 15 year-old.
Hell! I'm gonna join Stark on this one: Teens and kids shouldn't be playing heroes, they're too young for that! (And that's the only point on which I agree with Tony: I'm on Captain side.)
They don't have the mental strength to endure such large responsibilities.
Yes, there can be smart teens, but come on... Most of the time, they aren't.
New Warriors, anyone? =P
But if we're talking money, sure. All the kids love Spider-man.
And since we're talking about Disney, we already know what they seek more...