Hi,
Ah yes, I think you also need to remove the access level filtering on the MySQL query loading the prices from the database:
if(!hikashop_isClient('administrator') || (int)$user_id > 0)
hikashop_addACLFilters($filters, 'price_access', 'p', 2, false, (int)$user_id);
But then, you'll end up with all the prices all the time for all users, rendering the access level setting of the prices useless.
So it would need some PHP check to do the filtering on the access level, only when needed. You're looking at many hours of development ahead of you.
I don't think that doing it like that is a good solution.
A better solution I think would be to create a view override of product / listing_price.php and add custom code in there to run a MySQL query to load the other price when needed and then display it.