I've got a great news for you: those who buys 17" laptops aren't interested in the "light and vertical integrated laptops". They need the screen estate, they need a lot of [upgradeable] storage, they need a discrete video card. Guess who doesn't make these?
As an aside, go carry at least 1.2 for a full day and tell us back. Not your 'imma sit in starbucks and imitate cool hipster dev' but like a full day, especially commuting.
Though I'm not sure anyone can convince you of any of the points you don't want to accept, because they contradict the only true way of yours. Even if the people directly say what they don't need your vertically integrated laptop.
I've got great news: guess who makes the lightest laptops in the world? Know why they're so light? Vertical integration.
As an aside, if carrying 1.2kg is "exhausting to handle," I'm not sure what will convince you of any point on this topic.