It seems like we're more or less in agreement...Team performance and individual performance are interdependent, particularly in naive statistics like the ones you've mentioned are traditionally used. You're talking about making team-independent estimations of player value. That's completely valid. What I'm also saying is that in a similar vein, when you are considering how a player's addition will impact a team, you need to correct for his interaction with the team as well.
Yes, agreement! Thank you for nudging me to recognize that.
However, the studies I've seen (regular Fangraphs and BP reader) suggest these interactions between player skill sets is minimal, if such an effect can be shown.
Take lineup position. It's been studied ad nauseam, by some of the brightest in the field. Turns out, lineup order, over the course of a season, doesn't really matter that much. An intentionally suboptimal lineup underperforms an "optimized" one by maybe a couple wins per year. Almost all lineups actually implemented are more like fractions of a win, which is generally within error bars.
By and large, baseball is a game where you just assemble the best talent and they will win. (This is in regard to on field talent; I do not believe "clubhouse culture fit" is as silly as in the tech world, and is usually retroactively defined.)
