This is adorable!
 
Blue must be so happy! Who wouldn’t love to have that soft, squirming belly on top of them? The weight and motion of the shifting sac would be such a heavenly sensation. It would be so lovely to gaze up at Mulberry’s ravenous face, getting gradually closer as her struggling meals are broken down. You could even feel them softening as you rubbed against her belly.
 
That being said, being one of the ponies wriggling in her packed gut would be utterly delightful as well. Must be an interesting experience. Pressed against the stomach wall by the sheer mass of ponies, slowly digesting away, feeling something on the other side pressing inwards against you. Becoming a layer of soft padding on her middle would be the icing on the cake.

Ahhhh this is so good  
Swiftsketch you dun it