In this specific case, I imagine the system is much more secure. The Broadcom chip and Qualcomm chip each represented their own separate attack surface. Even without hacking the AP those chips were still a problem.

I would assume that Apple's new firmware would have been written in a memory safe language.

They did make some noise about enabling Swift for embedded development at last years WWDC.

Although Qualcomm's big zero day last year was related to the DSP and not the baseband, I believe.