Official bladeRF forum

Do you guys have any idea of implementing AGC using bladeRF Simulink blocks?
May I need to modify bladerf_source block to add input(s) for gain control?

I would advise you to design an AGC block independent of the bladeRF. This way, you can test and simulate it independently of the hardware first. After your simulations work, then consider collecting and using real-world data sets, as received by the bladeRF. Only once you have those working well, would I consider trying to run things real-time.