The placement of the cameras isn't actually that important, if you use them in a clever way.
Vauxhall (and there may be others, but I spotted that Vauxhall do this on a recent review video) for example have a single reversing camera on some cars and it can provide a top down view of the car as it reverses, with the missing images filled in with software non-live images. No idea what this is called, but
this (11:52 in) is where I spotted it working.
Land Rover clearly don't have cameras underneath the car, yet in their system they can produce an image of the road surface as it passes underneath the car
seen here (0:40 in)
Obviously, non of these images are 'live' but that's not a problem when generally speaking the objects around you are static during a parking manoeuvre.
Teslas already have a stack of cameras so I don't believe there would be many dead areas which would need to be filled in like the systems above do. Despite what is shown in the car, the forward facing cameras are wide already and the pillar cameras provide decent coverage of the forward facing side, some examples are shown in
this recent thread where someone was unfortunately in an accident and as a result requested their vehicle data from Tesla who provided the footage from all of the cameras, including
pillar and
wide angle front.