The modeler has not many options for tool integration, the models from Mapforce can not be imported in Mendix.
The only option I know is to write your model as XSD and import the XSD in the domain model. But I don't know Mapforce can do that.
In Mendix mapping is done with the Xml-to-domain mapping.
File a feature request for this, users will need this in the future, and it will ease the migration from other platforms.