Thanks for your reply, @bycrik
Yes I can modify the code of your plugin (it is very nicely written, by the way). But then I cannot upgrade the plugin in the future.
What about adding a WordPress filter to the product type in Frontend.php? Maybe accepting an array. So everyone could change the type using a hook/filter:
if ( $product->is_type( apply_filters( 'TierPricingTable_product_type', 'simple' ) ) )
in line 126 and 246 of Frontend.php.
