BTW - second image above doesn't load for me.
I'm afraid I'm the very least qualified to answer this (business aspect queries). The good news is, several here have done exactly that and are likely in a very good position to offer counsel. I don't think they'd see it as competition - people here generally have a pretty good idea of what they want, so it's either already available (in which case - there's a sale), or not - in which case, it's either in development, or just doesn't exist. But I still maintain that, for a niche group (always the case here!), this concept of yours would be fantastic. I count myself amongst those. Ever since I've seen this concept, I've been REALLY excited about it. My current S4 Mini is fantastic, totally love it - but it's not nearly as silent as I'd like. (Not the case's fault, obviously.) Knowing what I know now, if I had to do it again, I'd prioritize noise and allow the case size to grow a bit to accommodate.
For this crowd, I'd just say offer the case. A complete product wouldn't fly - I only know of one here, and while it seems to me to be a great product, it's perceived as overpriced (can't say I entirely disagree). If you offer the case and specify what its intent is, and what components go it's intended to be used with, people will gladly supply those.
For what it's worth - the Be Quiet! stuff is awesome. =) Even better if the case volume shrinks too!
One last thing : isn't the precise die location on the GPU critical for precise alignment of both coolers? If you're doing this for a broader audience, you might have to find some way to vary the GPU's position vertically a bit. (I'm assuming here that most GPU dies are centered 'vertically', when in a normal horizontal position - so that, in your vertical position, the GPU cooler wouldn't jut out to the side too much if one used a different GPU...if that makes sense.)
Keep it up - this is a rapid development cycle indeed. =)