You know, there wasn't really a need for the sequels.* Doc, you don't need to go to the future to get Marty and Jennifer's kids out of trouble. You can just warn them about it, thereby preventing it from happening in the first place, and let those two crazy kids drive to the lake in the 4x4 for the weekend. Because it is the future. I'm no mad genius inventor, but I am pretty sure that means "not happening yet." Start laying opposite groundwork in 1985, and 2015 can just, you know, be different as a result.
*But thank you! They are delightful! And I think III is underrated. Now, where is my Hoverboard?