Engines, it was once thought of many months ago, but it was never implemented, while this might make headaches its still a fun concept so here I will list out a idea I had in my mind for a while

Engines in this context would be multi blocks made with different components, with a sign on the crankshaft of the engine (more on that later) a player can register the multiblock with certain characteristics given its components.

Components of a Engine:

Crankshaft
The crankshaft is the core of a engine, engines can only built around a crankshaft, with different blocks giving different tiers upon which a engine can be built.
Tier I: Stone Brick (max 1 block length and only on sides of crankshaft)
Tier II: Iron Block ( max 2 block length and only on sides of crankshaft)
Tier III: Redstone Block (max 3 block length and can build in 1 block radius around crankshaft)
Tier IV: Diamond Block (max 5 block length and can build in 1 block radius around crankshaft)

Pistons
The pistons of a engine is where fuel is burnt to convert its chemical energy to kinetic energy.
Pistons can be put around the allowed build area of a engine, while having all pistons might give you great power, with no cooling it will explode when it’s too hot (more on that later) therefore engines must have a block to cool down the engine.
Pistons must be put next to the crankshaft. (No diagonal pistons)
Here are the limits for each tier of engine:
Tier I: 2 pistons
Tier II: 4 pistons
Tier III: 8 pistons
Tier IV: 12 pistons

Fuel Injector
Fuel Injectors are represented by cauldrons, they are used to boost the power of an engine, but this comes at a cost of very high fuel consumption, for every fuel injector the fuel consumption will increase by x1.5.
Fuel Injectors must be connected to a piston
Tier I: 1 Injector
Tier II: 2 Injectors
Tier III: 4 Injectors
Tier IV: 6 Injectors

Coolant Pipe
Coolant is important if you want your engine to not go boom, coolant will maintain the engine at nominal temperatures but they will run out over time, these need to be regularly refilled. The coolant pipe are hoppers and they contribute to the container count (if hoppers don’t contribute to container count normally, then this won’t too)
All coolant types will last for 30 seconds as long as the movecraft is piloted. Piloting will automatically consume 1 coolant unit and so does unpiloting.
Coolant must be connected to a piston or else it won’t work.
Coolant can be of such:
Ice
Water bucket

Heat sink
Heat sinks are filler blocks that can be of many types, they increase the time between going from 1 heat stage to another when coolant has ran dry.
Heat sinks are of such:
Tier I: Iron Bars (+0.5s)
Tier II: Tinted Glass (+1s)
Tier III: Copper Blocks (+1.5s)
Note: These values are per block basis, time can stack if there are multiple

Heat
Heat comes in multiple stages and each stage is increasingly worse for the vehicle.
Heat level can rise when there are no coolant pipes feeding coolant into the engine or there are no more coolant in the coolant pipes.
The time it takes to reach the next stage can be lengthened with heat sinks
Engine heat can lower very slowly when it’s not moving, so better to put coolant pipes eh.
Heat levels are of such:
Nominal (no negative effects)
Warm (20% more fuel consumption)
Hot (50% more fuel consumption, if hit by a shell will explode with the force of a charged creeper)
Burning (100% more fuel consumption, will explode within 20s of reaching this stage, if hit or time has reached will explode with the force of 10 charged creepers)
If coolant in every hopper is refilled, the temperature will instantly return to nominal. Filling only partial hoppers is not sufficient.

I know this idea won’t get implemented due to how movecraft on cancer is structured but at least it would make a fine idea