The shape of the body has a lot more to do than just ergonomics and aesthetics. Just because it doesn't share the same shape and an old VHS camcorder doesn't mean it's a poor design.
At the price point the BMCC lives, I would say it's mostly aimed at DSLR shooters who have "discovered" cinematic production who are looking to upgrade from their DSLRs. (more like stumbled
) I think that's a fair assumption.
DSLR systems are basically just a capture device. That's it. A sensor that can render a beautiful image and that's about it. Everything you might need/want for a complete system is something you need to add. Its a modular system. Traditional video devices, like the big Sony's, are designed to have everything you need in one body. 300 connectors, built in NDs, a menu with 100 options, viewfinders, massive battery packs, even the shoulder pad is built in! They are very different targets.
Black Magic has stated that their goal was to make a camera that produced the best image possible they could at that price point. So the obvious design choice is modular. Many DSLR shooters already have off camera audio, monitors, rails, etc. So make the best capture device and they can hit the price point they want. I think they hit that sweet spot perfectly!
The BMCC has the same shape and modular workflow as a DSLR. In comparison, RED is also a brick (and modular)...EOS C300 is, well I don't know how you would call it. It's definitely NOT traditional, but it houses many, many connections. Both of those seem to work quite well.
Yes, I can jump into 3DS and carve up a bitching looking design, but what does it do for ergonomics? Usabilty? Heat dissipation? 3rd party add-ons? COST? There are many factors to the design.
Lastly, if your clients are more concerned with your gear than your skill, then you haven't done a good enough job selling your expertise. Your clients should be confident in your ability to deliver a professional product. Henri Cartier-Bresson did a shoot for Vogue with a disposable camera. Shot 12 frames and handed the camera to the clients and said we're done. The photo ran on the cover. You should always be selling yourself, not your gear.