I've had this idea for several years (I don't remember if I've ever written about it here). This would be the most objective and rigorous way of quantifying the importance of players' offensive contributions.
The problem is that, in addition to the score, there are two other essential variables: the time remaining in the game, and league scoring context.
For example, a goal that gives a team a 10 lead at 1:00 of the first period might be worth 0.15 (hypothethically increasing the win probability from 50% to 65%). However, a goal that gives a team a 10 lead at 19:00 of the third period might be worth 0.45 (hypothethically increasing the win probability from 50% to 95%). This method would require a rigorous analysis of the win probability added based on the score in the game and the time remaining.
A more subtle (but equally important) consideration is the scoring context. A 21 goal at 15:00 of the second period might would be worth a lot more in, say, 2002, compared to 1982, given that the former season had far fewer goals per game, thus making each goal more important to a team's chance of winning. (Another way of thinking about it: given that there was so little offense in 2002, it's far more likely for a team to hang on to a 21 lead with 5 minutes left in the second period, compared to the wideopen 1982).
I spent some time working on this perhaps 78 years ago but gave up quickly after realizing how much work was required (also, the relevant data was much harder to find than it likely is today).
