So I heard a few hints that minecarts and probably trains in general are going to be released after the new clothing system. I looked at a few videos of mining-trains and ore carts and this gave an awesome idea. We should be able to customize our locomotives and or minecarts.Watch these videos :
Now what do all those minecarts and locomotives have in common ? They are more or less made from similar modules. The locomotives are all based on a flat 2-axle wheelbase with an engine and a seat on top. The carts are also mostly the same wheelbase with either a hopper or a flat surface for cargo on top.
So I imagine a system where we can craft maybe a few different wheelbases and then place different engine, fuel tank, seat, light, ... -modules on top to create a locomotive. Also it should be possible to make custom carts with chests, tanks for water, ... so you can bring all the equipment needed to mine for a while.