Semi-synchronous replication behaviour on statement or transaction

Feature Request:

One of our customers was asking if MariaDB semi-synchronous replication can do semi-synchronous replication on demand on per statement or per transaction level as MongoDB can do.

I was not aware of such a functionality and studied docu but I did not find any hint about this feature.

https://mariadb.com/kb/en/mariadb-replication-overview-for-sql-server-users/

Also the variables cannot be changed on a per session base but only globally.

So I checked MongoDB docu and there is indeed such a functionality:

https://docs.mongodb.com/manual/reference/write-concern/
https://docs.mongodb.com/manual/core/transactions/#transactions-write-concern
https://docs.mongodb.com/manual/core/replica-set-write-concern/

Feature request: Implement similar functionality like write concern in MariaDB (semi-synchronous) Replication.

Use case: In huge countries with shaky network connections this seems to be a need.