The problem with releasing it on blueray for PC users is that very few PC's these days actually have a blueray drive. That makes it a bad investment to have it printed on blueray. And regular DVD just isn't going to work.
That said, the size of the download probably isn't more than 100 gb, which will then decompress into 150 gb for the installation. So that's handled by letting your computer sit overnight and download. As far as disruptions and whatnot, the game is being released on Steam and GOG, and both of those have clients that can handle the download and installation process. I believe they download in chunks and assemble at the end, so they should be able to handle interruptions to your internet service.
By the way, 4 min per gigabyte is 240 seconds per 8 gigabit or 30 seconds per gigabit or gigabit / 30 per second. That's a 30-40 mbit connection. I'm not sure it's reasonable to call that slow, even though some people are spoiled potatoes sitting on fiber connections. And I don't think you're going to get a whole lot faster than this through a copper connection.
