Changes will be better in the long run
There were A LOT of changes in the first 10 minutes of S4's premiere. But! I think they're all for the better.
First, Rachel King's character needed to go. She took screen time away from F&B. And let's be honest, her acting wasn't stellar compared to the rest.
Second, Karp is much better as an adversary, rather than a partner. Allows for more pointed and purposeful interaction between him and F&B.
As for Pindar and Karmen, hate to see them go, but at some point their story development was running out. Having them living with F&B made it semi-important for them to be seen a good bit, and thus, thrown in the mix. I am not sold on the new PI, but with him not living with them, there's no need to see him all that much.
In the end, changes will be better for the show. We get more F&B and that's fine with me.