The reason front bumpers cause the Adaptive Cruise Control and Parking Assist Systems to go haywire has to do with how those systems work in the first place. Both of Ford's systems use radar to gauge how far objects or other vehicles are from your front end. The radar system is mounted in the 2015 F150's lower bumper behind one of the "breadbox" humps. While the radar can penetrate the fairly thin plastic of the bumper itself and pick up a radar return off in the distance, it just reflects off of the steel that makes up the vast majority of the off-road bumpers we offer here at Stage 3. The end result is that your truck thinks its inches away from crashing into something at all times, making both Adaptive Cruise Control and Parking Assist absolutely useless if you add a bumper.
As of right now, there's not currently a set way or kit available to locate the radar systems for Ford's Adaptive Cruise Control or Park Assist. Maybe a pretty hefty wiring job and some custom fabrication could solve the problem, but your safe bet may be to skip on a front bumper for now if you have these systems on your truck.