It doesn't render all your privacy moot. It's limited to snooping on what you send over the radio, which is the same as what your cell carrier would have access to even with a secure baseband. (Edit: unless the baseband hacks into the software running on the other side of the radio and exfiltrates data right from your SD card... hm...)
What I would like to see is a way to verify that you're connected to a legitimate cell tower and not an eavesdropper.
In many/most phones, the radio can access the ram of the device(DMA). the reason is efficient transfer of data, but with that comes the possibility of the radio reading everything inside the ram, including encrytion keys.
Not necessarily - some processors (Snapdragon, for example) implement the baseband right into the core processor -- it will have more access than just the radios. I'm pretty sure the baseband also has access to the memory as well, right?
What I would like to see is a way to verify that you're connected to a legitimate cell tower and not an eavesdropper.