@box464 still too hacky. This is in fact like the inversed version of keyword filtering but for specific accounts.
Even if this is implemented (on Mastodon or any mainstream platforms), it'll probably take time for people to shift their mindset over this. Another problem that someone mentioned is that the hashtag following won't work for boosts, if say, boosting music-related posts, which may not be hash-tagged, from a music-interest account.