@jebbench I created this PR to address the issue: #345
Can you please check if it solves the problem for you?

The updated interfaces look like exactly what I'm after; I've not tried it in practce though - is there an easy way to do so?

You can checkout the related branch and try testing your use cases.
To try it in external projects you can install it to you local maven repository (mvn install -DskipTests=true -Dgpg.skip). Before this, to avoid overriding maven artifacts, change the version in the pom, to something like: <version>6.6.4-SNAPSHOT-PR345</version>.

@rashtao I can confirm this works for me! Cheers for reacting so quickly and for the patience with my slow responses.

getCollection(client)
    .updateDocuments(
        it,
        DocumentUpdateOptions().keepNull(false).mergeObjects(true).returnNew(true),
        clazz
    )
    .await()
    .documents
    .map { it.new }