Non-Stop Bullet Train Concept

Or do like Brazil and collect all the fares for trolleys while on the platform and have a bunch of doors open so everyone boards and exits at the same time.
In this concept, obviously people have to get out of the upper pod to continue and enter it to exit and the station track would have to be much longer to skip the losses speeding up and slowing down.

Actually, the Japanese shinkansen system long ago provided the solution. Three different speeds of trains. Super expresses that stop only in the main cities, medium speed trains that stop at moderate intervals, and locals that stop at every station. All the schedules coordinate so there is not much more than 5 or 10 minutes or so to wait between different train classes if they both stop at the same station, and usually switching from one to another only requires walking to the other side of the same platform.

If you travel shinkansen by the slower trains, you will often find yourself waiting at the side platform of the local stations a minute or so longer, while the faster train overtakes you without stopping. The local then takes the "slot" behind that train on the same track.

It all works beautifully.

In practice you take the fastest train for the bulk of your journey, then hop over to a medium or local for the last portion, if you are going somewhere more out of the way.

Play around with some destinations here, and you will see how it works. Eg, Tokyo- Maibara (one stop before Kyoto)

Nozomi=Fastest
Hikari=Medium
Kodam=Slowest

http://www.hyperdia.com/classic_en/hyperWeb.cgi

Dangerous, and requires a complete new infrastructure. Not to mention tunnels and bridges which will need complete rebuilding. Plus all that metal and people up high make the whole thing less stable. Ice and rain will make the mechanism unworkable. Here is a better idea.
Its a train right? There are separate cars. Power each car with its own motor which does not need to be as powerful as the main bullet train motor. (you will see why in a moment.) As the train moves into the station, the last car in the train drops off, and rolls to a stop, and the passengers depart. Then the empty car can be sent to the end of the line at its own speed. The main train continues on to its final destination without any delays. That takes care of drop offs. Pickups of passengers would be just as easy...the loaded car would be brought up to speed by catapult (like a carnival ride) and would be picked up by the next train coming down that track either by docking in front (risky) or by linking up behind (requires a siding)
The picking up of passengers would be a little riskier, but a reasonably competent engineering body can make it safe, and like all trains, it would be very fuel efficient.

Of course, if the run was a fairly short one, say, under a thousand kilometers, then what is the fuss about an extra couple of five minute stops?

Why not have the shuttle train horizontally separated and not vertically separated. Just have a normal self powered electric carriage on a station siding, load with passengers and time it's departure to synch with the large train and link up, unload its passengers to the fast train, then load departing train passengers, uncouple, quickly move to a siding, and and slow to arrive at the next station. No fancy elevation, just extra sidings for stopping and starting the shuttle car.

This looks like a number of accidents just waiting to happen. Should be great for the lawyers!