A little confused here. Steam as DRM has been proven ineffective, but that's okay because at least they tried. Disc Check DRM has been proven ineffective, and therefore cannot be used. Is there something I'm missing?
If it was a recently developed, actively supported disc check function it would suffice. A "simple disc check" the way it used to be done is so out of date that it can't really be said to be a real attempt to protect the product. It obviously doesn't have to be Steamworks as a lot of companies have DRM software that can be licensed, but it has to be something still being supported.
As to the share holders, I'd just say "Well we can spend millions of dollars on an intricate form of internet DRM that, ironically, can be easily bypassed by anyone with an internet connection. Or we can put that money back into the project for development/advertising/merchandising."
I suppose if you got them to sign off on it ahead of time that would be fine. Unfortunately, the most likely place for you to be saying that would be in court while defending yourself from the lawsuit. Of course, if your company is bringing in enough money the shareholders won't bother you....until things go bad and then they'll sue you.
Yeah, I'm a cynic about investors.