For a student on the +2 math track and doing well enough to consider calculus BC in 11th grade (i.e. a very strong student in math), taking a calculus course less rigorous than calculus AB makes no sense.
If the student decides to back off on the overall rigor and workload, and math is the place she does that, then changing BC to AB makes the most sense, not going down to a sub-AB-level course (if the high school even offers such a thing).
Statistics will be useful in any social science major. Some students who do heavier statistical analyses may find calculus useful as a prerequisite to calculus-based statistics. Also, if the student majors in economics or wants to take substantial economics as a supplement to another social science major, calculus is likely to be necessary.