You made a lot of good points, it is a pity that I don't have enough time to discuss them in detail.

Just a short note:

The main difference between my and your approach is that I start from HL as the main example and you start from Baldur's Gate.

Your player as a co-author may work for games like Baldur's Gate, but it doesn't for HL. In HL you don't have a choice, no selection of the charakter and no moral decision. You have to escape and survive, and you've got complex but linear levels, with only one entrance and one exit, that's the restriction.