Is your enhancement related to a problem? Please describe.
Yes. When our admins are supporting customer subscriptions, the ElasticPress search functionality doesn't "take control" for the WooCommerce subscriptions interface (wp-admin/edit.php?post_type=shop_subscription).

Describe the solution you'd like
In the same way that Feature/WooCommerce/WooCommerce.php does the remove_action against WC's search_custom_fields, it would be great to takeover WCS' shop_subscription_search_custom_fields action in a similar way.

Describe alternatives you've considered
I tried to write this myself as a GitHub gist, but there's no hook on the translate_args to add 'shop_subscription' as a indexable post.
Likewise WCS' class-wcs-admin-post-types.php isn't very adjustable, so I couldn't modify that functionality without going into the plugin itself. If it turns out that plugin functionality needs to go into WCS, too, then I can submit that request to them.