Hey, this is my "Minedea"

Connectable Mine Carts. Basically what it does is make it an easier way to transport all of your storage/furnace/normal mine carts in one go! The front one would be the main leader one, basically meaning that it would make all the force, so if you go over a powered rail, the first one touches and all the rest don't have to, to go. To craft a hook (The thing that will connect the mine carts) would be three iron ingots on the bottom three cubes on the crafting table, one iron ingot in the middle of the crafting table, and 2 either on the left or right on the top of the crafting table) his could also introduce ways to steer mine carts, so if there were two different ways to go, you could hit A or D to move left or right, it can also add new mine carts such as a powered mine cart, very pricey, a mine cart made out of solid diamonds with redstone in the middle, and three furnaces on the top, it also takes coal to go. Another mine cart could be a movable mine cart, using the idea to steer mine carts, only this one could be the one that turns, it would also have to be in the lead to turn, the crafting recipe to this would be gold replacing iron, then sticks in the empty spaces (Steering Wheel)

This could end up making mini-games where you have to steer your mine cart out of trouble, it would also introduce cheaper ways to transport mine carts using the self propelled mine cart, it would be an investment, but end up making you more money.

This would be a great improvement on the game, because it would make an easier way for you to transport your mining goods to point A to point B without having to make several trips. It can also potentially make new redstone contraptions. I think if mojang added this in, people would use mine carts more often!