Hello Maxime!
I'm currently working on an improvement on btree_gist and Andrey suggested that maybe I could ask you to check my proposal[0] since you're modifying related code. Would you be open to it? Any feedback would help me!
Regards
[0] - https://www.postgresql.org/message-id/36b4f67d-5975-452c-a6b8-b6407f0924ee%40Spark