Changing the style is easy: Just feed it a writing sample, and tell it to review its own writing against the style of the writing sample.

That won't entirely weed out these tropes, but it will massively change the style.

Then add a few specific rules and make it review its writing, instead of expecting it to get it right while writing.

To weed out the tropes is largely a question of enforcing good writing through rules.

A whole lot of the tropes are present because a lot of people write that way. It may have been amplified by RLHF etc., but in that case it's been amplified because people have judged those responses to be better - after all that is what RLHF is.