Interesting concept but not technically required in my opinion.
Merging them together will not practically make it any more "organised" as has been described, what makes organisations work effectively together is the attitude of the employees of said organisations, and how they choose to interact with one another.
I haven't personally got a problem with the SAPD, FBI etc being totally different divisions. It's not a terrible idea for both organisations to be accountable to an individual (or government), but both serving under the ARPD banner? Meh.