Several of your points could just as easily be used to argue against your position.
The phrasing we're discussing is used by many, so if language is by its nature shared, what elevates your preferences over those people? They share that usage, after all.
Secondly, you mention misunderstanding, but the "intrusive of" is not ambiguous, it does not make the phrase more difficult to understand (even Garner calls it superfluous but not misleading), so why would misunderstanding even come into this particular discussion?
Finally, "new features should be added with care, and only if they serve a purpose": language isn't engineered, it develops, so adding anything on purpose, with or without care, simply doesn't come into it. Serving a purpose, though? If people go for one usage over another, it obviously serves a purpose for them, even if this purpose may not be readily apparent to them or to you or me, whether that purpose is rhythm, the phrase's proximity to other constructions, or anything else. Unless the implication is "only if they serve a purpose to me personally and the people who share my views", which again would privilege the sharing of one group over that of another, without much justification.