Magento 1.7 – Set Image as Base, Small, and Thumbnail

Here is given programmatically adding media images to product, you can adjust this code to your own importing script:

    $mediaGalleryAttribute = Mage::getModel('catalog/resource_eav_attribute')
        ->loadByCode(Mage_Catalog_Model_Product::ENTITY, 'media_gallery');
    $mediaGallery          = $mediaGalleryAttribute->getBackend();
    $attrCode              = $mediaGalleryAttribute->getAttributeCode();


    $product          = Mage::getModel('catalog/product')->load($productId);
    $mediaGalleryData = $product->getData($attrCode);
    /**
     * If you want to remove old images use this code
     */
    if (isset($mediaGalleryData['images'])) {
        foreach ($mediaGalleryData['images'] as &$image) {
            $image['removed'] = 1;
        }
        $product->setData($attrCode, $mediaGalleryData);
    }
    /**
     * Here is real image file path
     */
    $thumbnailFile = 'real/path/to/thumbnail/file.jpg';
    $imageFile     = 'real/path/to/image/file.jpg';
    try {
        //Set thumbnail
        $imageFileUri = $mediaGallery->addImage($product, $thumbnailFile, null, false, false);
        $mediaGallery->setMediaAttribute($product, 'thumbnail', $imageFileUri);

        //Set image (or base image, small image whatever you want
        $imageFileUri = $mediaGallery->addImage($product, $imageFile, null, false, false);
        $mediaGallery->setMediaAttribute($product, 'image', $imageFileUri);
        $product->save();
    } catch (Exception $e) {
        Mage::logException($e);
    }

And to answer the question: No, magento can't do this out of the box. But you can "easily" change the JS code which adds the row to the table, so when you add the first one, the radio buttons are checked.

The creation of a row is made here: js/mage/adminhtml/product.js:140