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?