You can indeed go pellet-less but I think you would need to make sure that the buns got a huge amount of forage with lots of different plants in there to make sure they get everything they need. In the wild they primarily live off of grass but will have access to a huge variety of other plants mixed in with the grass, in hedgerows, down the sides of footpaths ect ect. It's these other plants that provide the bun with a lot of the vitamins and minerals needed to keep healthy.
The beauty of the pellets is that they contain many of the nutrients that they would naturally find wild in a condensed form so that when fed alongside oodles of hay you know that they are getting a balanced diet. I feed pellets for that peace of mind (and because if I didn't they would pine because they LOVE their food :roll
I also feed lots of forage but barely any veg as I think it's more natural for them and also raiding the local footpath or even the garden is much cheaper but just as popular than veg!
They really don't need much pellet food, about an eggcupful a day per adult bun, it the most important thing to do is make sure that whatever you change their diet to you need to do it slowly and gradually :thumb: