More weight stages would be great but, I really suggest you subdivide the weight stages before adding new ones. And a progress bar would be great.
imho adding more activities to do, would be the way to go in the next update(s).
Many further weight stages are not that important to me - maybe one more at the top weight and one more on the skinny side would add a nice touch tho.
Subdividing the current weight range would be cool but might also be a ton of work.
Let's see what the next update, announced as beeing "Quadruple!", brings :)