I'd just put up with external cable routing until the bottom bracket needed replacement. In fact I don't think I've ever had internal cables, despite using a variety of dynamos over many years. But as long as you're sure that's a press fit bottom bracket ...
I can't quite tell - is the bearing retained by a small lip on the black part? I wonder if it's waiting to pop out and could be encouraged by resting the black bit on a wooden block with an appropriately sized hole, rather than trying to support the frame and knocking the whole assembly out. That might make it a less bad design than the one in the video you included.