Using dynamic_reconfigure with the base_local_planner requires a fairly
extensive patch to the code. If you're up for attempting it, I built dynamic
reconfigure support into the dwa_local_planner package that you could use as
an example, and I'd be happy to take back and review whatever code you
write. Without modifying the code, however, I'm afraid that there's no way
to have dynamic reconfigure affect the base_local_planner's parameters.