Thank you so much kind person :)

Hey anon! It never notified me of this message :O thanks for the compliments :) it is certainly possible to bulk up a doll. You can use air dry clay to add to the body just remember it will be delicate. The only way to really make it durable would be to sculpt it then make a mold of the new shape and cast torsos out of plastic (like some of the people who have made torsos with two necks, etc) that takes a lot of work and materials though. For light play or display air dry clay from a local hobby or crafts shop would work just fine :)