I'll keep this a short as I can. For a biological worldbuilding exercise where humans possess far greater biological abilities. I imagined a pancreas-sized organ that contained a huge reserve cache of dehydrated stem cells, and whenever there is any injury the body demands massive amounts of water to hydrate and mobilize these stem cells to go and fix the problem.
I did some light research into this problem and it told me that there really isn't any HUGE problem that ends up stopping things like limb regeneration, and traits like these haven't evolved purely because the chances of surviving a wound that requires a huge reserve cache of stem cells is so small that its just not worth it.
So I was just looking to get some feedback and consultations on the biological problems and challenges that it would face where it to be real?