Currently, we are using Cloud-init 18.5 with some portion of our home-grow changes for modules. To provide better compatibility with all modern changes in environments there is a sense to update Cloud-init itself to some more modern version.
Also, after the changes from T1987 / https://github.com/vyos/vyos-1x/pull/218 it is possible to drop changes for Datasource modules, which forces calling dhclient and use a native Cloud-init way instead.