Adding refinery CMS to an existing application that uses mongodb.

Scenario

An application has already been written, tried and tested without a CMS, I want to add a CMS to the application.(refinery if possible although can be anything else if it would be easier).

I have done the application using rails 3.1.1 and I have used mongodb for the database which has made life difficult as all the CMS's such as refinery and radiant require SQL database.

Ideally I want to leave the application logic alone and just override the views with a CMS.

The application logic is all handled in the models with the controllers just acting as handlers.

What options are available to me to add a CMS.

Some ideas I have had are.

- place the built application as an Engine of my refineryCMS application and override the views with refinery CMS

- roll my own quick and nasty CMS that stores editable html in a SQL database and call this in my views to be displayed.

- Re-write the application with a CMS in mind (not my favourite as this will take a lot of time.)

Any thoughts and ideas much appreciated.