Cossette was a supernatural horror story about idolizing a subject (or maybe artistic results would be more accurate) rather than the IRL horrors of delusions (or aspirations, depending how you look at it) of artists, their art and people close to them (presented in a very off-beat manner) so I don't know if I'd compare the two.
I just watched Achilles to Kame and liked it more than most of the Beat Takeshi movies I've seen. Having listened to the soundtrack before watching the movie, I was expecting more of a straightforward drama and was prepared to be bored. But it was a lot more interesting, absurd, and sardonic than I expected. Although Yuki's score is pretty and low-key and works fairly unobtrusively in the movie, I think the gentle, sentimental, and nostalgic mood of the music doesn't quite fit the off-beat, ironic, and cynical tone of the movie. Although maybe this clash was intentional. I'm also curious why Yuki hasn't worked on more live action films.