Jane pointed you to my thread. I've been through various stages of pelletless diets and am now happy at feeding them pellets twice a week.
It's the done thing in some countries, not feeding pellets. Some piggies thrive without pellets while others don't. It all varies so much, the only way to know is to try. Reducing the amount of pellets fed is good enough, in my view, to turn the diet around to a more natural one. You don't have to entirely withdraw them from the diet to encourage a more natural diet - you can feed more types of hay, a wider variety of veggies, include grasses and wild forages - and those will naturally be off more interest and importance...the pigs usually prefer all the fresh stuff!