Changing carousel widget (ajax)

I successfully changed the way carousel loads content by using siteorigin_widgets_template_file_sow-post-carousel filter.

Now I would like to load the content the same way also when loaded with ajax. And here comes the part, where I am not sure if it can be done in a proper way.

I could do it by changing the sow_carousel_get_next_posts_page() function, but this one is in so-post-carousel-widget.php file within the plugin’s folder.
However I want to keep the plugin upgradable, and not change the plugin main files, I want to keep modifications inside the theme.

It would be fairly easy to modify functions if they would be wrapped with “!function_exists” ie:
if ( !function_exists( sow_carousel_get_next_posts_page() ) ) {
sow_carousel_get_next_posts_page() {
…
}
}

Is there a way to load my own function instead of sow_carousel_get_next_posts_page()? If not, would you be willing to release an official update of the widget bundle which would allow such customization?

Thanks