How to implement many-to-many relationships in Sonata Media Bundle

I am trying to relate SonataMediaBundle to another Entity: Products with a relation ManyToMany.

The schema and relation are well created.

However, when I edit or create a new product, I try to add a button where I can search a media file through the media library and a button to upload a new file.

For a relation OneToMany, this is easily done in Admin\ProductAdmin::configureFormFields by adding:

->add('image', 'sonata_type_model_list', array(
                    'required' => false
                ), array(
                    'link_parameters' => array(
                        'context'  => 'default',
                        'provider' => 'sonata.media.provider.image'
                     )
                ))

So I get the same 3 icons as they already been used in the Gallery of SonataMediaBundle (add from library, upload and delete)

BUT on the relation ManyToMany it isn't possible! Because every time I choose a media, it replaces the previous one. So I can't select multiple media types.

I thought on using the same way as The Gallery (galleryHasMedia)

->add('galleryHasMedias', 'sonata_type_collection', array(
            'by_reference' => false
        ), array(
            'edit'     => 'inline',
            'inline'   => 'table',
            'sortable' => 'position',
            'link_parameters' => array('context' => $context)
        ))

However, it is really complex. How can I choose or upload multiple media files on another Entity through a ManyToMany Relation?