I have to agree with Jokiin- today's smaller wedge cams can be very discreet and fit well in modern cars. They don't always offer the best solution though, which is why the different form-factors exist. Even remoted cams like the K2S with it's tiny lens modules aren't going to work for everybody. Part is in how and where the cam is installed and part in what you want from it.
The real problem here is that cams come in only one form-factor, so if you want the vid quality of an A129 Plus, you have to accept the wedge form factor it has. If you want the cloud connectivity of the DR900X you have to accept the tubular form-factor it has. Calling for a specific form-factor is going to limit what you can get from a cam, which may be acceptable if your only goal is to have reasonably decent video images. There's nothing wrong with that approach either; it's just a path fewer people take as for most it's the cam's features and performance which matter most.
Phil