Workflow and revisions

I'm currently working on a Drupal installation where they would like to implement a workflow. For every page, they would have to be able to set which group of users can edit it, and which group should approve the content.

The workflow module is installed and there are 2 states defined: "Create" and "Publish". Only the approver role can change the status to Publish and then there is an action executed to publish the node. The default publishing option is set to:
[ ] Published
This way I make sure that newly created pages are not published until someone of the publishers changes the workflow state to Publish.

Since the workflow can only be defined on level of node type, I have also installed the module nodeaccess, to be able to define for each individual page which role has the right to edit the node.

This seems to work fine, but I now have a problem with revisions. Every time an editor makes a change to the original content, the newly created revision should be approved first, before it is published on the website. While the new revision is not approved, the old version should remain published.

I have tried to achieve this with the module revision_moderation, but that doesn't seem to work.
I put the default publishing option to
[X] Create a new revision
[X] New revisions in moderation
but when I edit the content as a content editor, the revision is never created and thus doesn't appear in the "Pending revisions" queue.

Can anyone help me out on this? Has anyone created a similar workflow yet and has experience on implementing it?
Any help would be very much appreciated.

Thanks
Koen