The solution here would be to set the manipulator/solve_type parameter in the private namespace of the move_group_commander_wrapper before it gets instantiated.
I haven't looked at how the Python wrappers for the move_group_commander are created, so I don't know where the _1499261351880510562 suffix comes from. I suspect it's a Unix timestamp, which is typically added when nodes are created with anonymous=True as one of the arguments.
If that can be left out, then you should be able to first set the required parameters (using a launch file), and then start the node that instantiates the move_group_commander_wrapper. That should allow you to set the solve_type parameter.