If the camera is not going to contain the A2D hardware, then we shouldn't bother talking about such things here, it will just distract from talking about the camera.
This does not mean we are not interested. I am interested in smaller and cheeper, currently I spend about $600USD for a used Panasonic AG-HMC150P.
I am sure you are curious, so here is how integrated hardware solves the following issues that I can think of.
delay config: We sometimes do use separate audio hardware, and we are able to work out the delays to accommodate the different latencies so that everything remains in sync. The problem is different hardware has different latencies and it isn't well documented so changes risk problems that are not quickly solved. Integrated audio means never having to think about keeping the two in sync.
quality: typically the A2D on a camera is better than the typical usb audio device. the cameras we use have compressors, so clipping is almost non-existent.
hardware deployment: the number of components for a typical setup is enough that it takes significant time to assemble, and it is more than a person can keep track of in their head, so inventory management and check lists are part of the process. Integrated audio means less things to pack and assemble.