Elder stage
So my idea for this system is once you hit adult you would unlock a new stage called elder which will appear as a pop saying begin elder.
You would begin and it'll be a new stage but it'll take twice as long to hit elder buy you will gain 10% combat weight,5%extra hp but lose 10% stamina as a result of it.
It'll encourage people to grind and quest more with a reward for hitting elder being a skin and a achievement called "born survivor"
Model wise it'll only be a slight size increase and small model changes e.g eos horns being longer and rexs ridges being more defined.
Hopefully this gets considered!