I think Jeb purposely do not want to push containers (chest/furnace/dispenser) as this will involve in complicated calculation in the inventory attached to it which will also increase the workload of the game engine.
Especially these things are to be designed in SMP environment. The flicking of redstone signals is already a framerate killer for SMP and I don't think the developer wants more things to be calculated for no meaning.
There is one thing I think the texture of the piston is somewhat incorrect - blocking water. Shouldn't it be sealed to the side so that water would not passed through/destroy the piston?
Anyway I am having lots of idea on how to play with the piston. Piston that cover the light source, piston that pump water upstream, piston that...
My 2 cents.
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Here is the schematic of my arrival station.
First is the idle state where no cart is coming in:
A recycle cart will spin at section 1 as indicated at diagram above in green.
Section 2 is open.
Then, when minecart carries someone come in and land on the pressure plate:
The pressure plate will send signal via redstone circuit to open section 1 and close section 2.
The spinning recycle cart at section 1 will be release to section 2, and will be spinning.
When the guy leave the cart, the redstone will send another signal to close section 1 and open section 2. The recycle cart on section 2 will come over and collect the cart.
The recycle cart, will go back to loop section 1 and the entire system is reset.
I do not draw out the actual implementation as it varies between north/south/east/west facing but the general idea is there. Also, separate booster track are required in section 1 and 2 for keeping the cart spin.