It would be costly and troublesome to redesign the case at this point in time, but it may be worth considering in future cam designs. I've noticed that there are two threaded inserts with this cam; one on the side just above the SD card and the other centered on top. Not sure what their function is but perhaps could provide a means to mount the interior cam to the main body through some kind of adaptor? Or maybe alternative means for mounting the cam (without GPS as that's in the mount)? I wonder why they are there- anyone know?
Having said that I am not sure if the approach of an integrated mounting is truly good. It will increase the bulk of the main cam to attach the interior cam this way, and as always different cars need different mounting positions of the main cam so one attaching point will still not work for everyone. And with most cams that have a "plug-in" style interior cam (as well as this one as it is now) you get only vertical movement. I'd like to see horizontal aiming too, and that will need a new mount for the interior cam. "Wedging" will work for most installs, but after having the B2K I very much like that I can aim it's interior cam wherever I want to with just a quick twist with the fingers. It is by far my favorite feature of that cam

As the A139 is now you can stick the interior cam where you like already so it's not really a big issue but more of a possible design refinement.
What I think should be done here is to
offer different cable lengths to better handle the different installs. This is already appearing to be important even with the limited number of these cams being used right now;
if we're having issues with this in our few numbers it will be a much bigger issue on the open market
This could be handled in a number of ways. There are lots of cable-makers offering coax with fitted connectors in every variety now, so to avoid the need for extra stock or the hassles of shipping additional items
Viofo could recommend a specific seller where buyers could go the get different cables they need while ensuring that the necessary quality is still there. That would make it easier for Viofo and allow every buyer to easily have the exact cables they want incliding straight or angled ends

I'm sure that in time someone is going to find and share a source for these cables anyway. That's on my bucket-list but I don't have time to look into it right now or any time soon.
Phil