General Idea: I've been thinking about this for a while now. It's hard to move large amounts of items, and especially resources, long distances quickly. How about trains? I've noticed that techy stuff is not what you guys are going for, so a player powered train could work.
Features: You could have a train construction platform, where players can attach chests, pallets, etc. However, everything will have to fit within a certain area on the platform. Personally, I would limit the number of cars to 3 or 4 just to avoid lag.
Construction: A track system made of weed stems, crude rope, and grass planks. Each car could have acorn top wheels, and have grass planks for the floor.
Fitting it in: Maybe this could be a part of a larger update that includes gears and the like, opening up the possibilities for more machines.