I have made it no secret on Twitter that I have been playing a LOT of a game on Steam called Terraria. I highly recommend it. It's only $10 and I have been playing it for getting close to two hundred hours now.
Terraria is a game much like Minecraft; the goal is to explore and gather as many resources as possible to create bigger and better armor and weapons to help you survive the horrors of the world you are stranded on. While Minecraft is a 3D game, Terraria is designed much like a 2D platformer.
So how does something like this translate into a pen and paper RPG? The short answer: resource management. Good, Lord! I could hear some of you shudder as I'm writing this! Resource management has a bad reputation in the RPG community. Very few people actually bother to keep track of everything they eat, collect, and sell. Weight capacity alone has become one of the most ignored mechanics of any given RPG.
If you somehow manage to trick your players into using resource management, you can then begin the process of Mining and Crafting. Now, mining doesn't exactly have to be about digging into the earth; it can be any kind of gathering that requires at least some effort. This means that you could be collecting anything from gold ore to bear skin. The fact of the matter is, you need materials to construct greater devices out of.
If you think you can handle the math for weight capacity, go for it. Keep up with each item you collect and, unlike Terraria, make use of wagons and carts and BAGS OF HOLDING. Good Lord, Bags of Holding will help you so much here.
If weight capacity is too much of a hassle, perhaps we should look into an inventory system similar to the video games of our era. Using Dungeons and Dragons 4th Edition as an example (what can I say, I'm a fan), the maximum for a normal load is Strength x 10, for a heavy load it's Strength x 20, and for a dragging it's Strength x 50. So, since video games usually use slots for equipment, let's say that a character has a number of slots equal to Strength x 3, each slot approximately 5 lbs. worth of equipment, including money. I just made this up on the fly. Lemme know what you think.
Now, once you have your materials, it is time to start crafting. It's best to know exactly what you want to make before hunting for the materials. You can decide whether or not to craft the material yourself, but having an NPC do it is, while a time saver, more boring...in my opinion. Using 4th Edition as an example yet again, I would use Strength based skills to forge metals and Dexterity based skills to craft other types of things. Perhaps you can create decent designs using Intelligence or Wisdom.
I would not recommend doing this if any of your players hate resource management. Good luck because in my experience, that's all of them.