If they are planning on introducing the X-Men next phase, I think they should introduce Iceman as a student at Peter Parker's High School, whose powers manifest when he gets attacked, and Spiderman helps him deal with it. Perhaps add Firestar as well, with her and Iceman helping in the final battle. Then at the end of the movie in the end credits they could have Professor X show up with Cyclops to recruit Iceman for the X-Men.
This would add to their history they already have together, and create a relationship to play off of later during a big phase end get all the teams together blockbuster.
What you think?
How would you introduce Iceman to the MCU?