This is a really simple challenge, its just meant to make minecraft a little more realistic. The main idea is that if you die its over, thats fairly simple. The next thing is that you dont have some super backpack that holds enough items to make a mansion. You can at most hold three things. Playing on peaceful is discouraged because you heal in ten seconds, though monsters arent realistic you can keep them around or take them out of their files and make a mod for this.
Easy mode: You can hold one full stack of items and three items (ex: sword and pick), and can play on easy or peaceful.
Medium mode: You can hold 20 blocks total and two items, and play on normal or hard.
Hard mode: You hold 10 blocks total and hold two items total, must play on hard.
Your main goal at the beginning is to make a chest so you can store the things you cant hold. This makes mining, building, and adventuring a lot harder, since you can't take to many things with you. If you want to do those things you have to bring a chest so you can place items in it.
Tell me what you guys think and if i can add anything to it! Any ideas are welcome so dont hesitate to say!