I think a system for character aging would be cool. The Base Idea is every 5 Minecraft days you grow 1 year older this could easily be handy for many things. You you would start off as a 10 year old, You can gain experience in different classes as well as slowly become stronger. When you reach the rare age of 50 something you will become weaker but your experience will triple as well as new crafting recipes will unlock. This aging system can also affect animals and food (not only the player). Animals can age and die, well food can go rotten. I think this feature could be a nice addition to Minecraft, as well as give a pinch of realism. When you die you go into a creative mode like state, with a bit of no clip (But this will only ac-cure when you die of old age...) then you can either reincarnate or stay a ghost. I would like to see this in the form of an actual feature or mod, for Minecraft but I'm not raising my hopes too high ...
Thanks for listening - SpraAnt