The short: It's not needed
Okay I am a freighter pilot and would LOVE this kind of idea, but at the same time I have to say that it is not 'practical' nor is it 'realistic'. I say this because we have to consider some general ideas as far as physical space and real life conditions.
First, some basic numbers.
The most commonly used size standard freight container in the world is 40 feet x 8 feet by 8.5 feet, which after some conversion is 100.75 m3. A fully loaded container will weigh roughly 29.5 tons (each ton weighing 2240 pounds/1016kg)
A typical freight truck will have 1 of these size containers.
A moving van, half that.
Your next door neighbors truck.... lol
But what about a train? To start, trains have less to do with dimensional size and more to do with dead weight (weight that the earth pulls as opposed to weight being acted on by another force). But all things being equal, a 600 horsepower single engine train will be able to pull roughly 6000-10000 tons before needing 'helper' engines. A typical freight car will weigh between 20 and 130 tons. We'll just use averages and say 8000 tons capacity, each car averages 80 tons (2 fully loaded, max weight, freight containers, double stacked and locked, plus the car itself). That being said we can have 100 cars, or 200 freight containers.
So what does it all mean? A single engine train will haul roughly 200 of the aforementioned containers of roughly 100.75 m3. Meaning 20150 m3.
A freighter (caldari charon) can haul with max skills 981250 m3 or the equivalent of 48.7 of the trains in the example.
Now please understand that the example is only a single engine. What about multi engine setups? Now we are in the realm of massive amounts of weight, but to give an idea lets take another example.
There is a coal train that has a LOT of engines..... a lot. Those engines pull roughly 500-600 cars. We'll for our example say 550. But the cars themselves weigh in at 130 tons. So if we do some math and work backwards (reduce weight per car to 80 tons, giving us 50 tons per car to add more cars) we add another 344 cars, putting us at 894 cars, or 1792 freight containers or 180544 m3 of space.
The same freighter (caldari charon) still has the equivalent space of 5.4 of these trains.
So folks, we're already flying a train. More than a train, in fact. If you've got THAT MUCH stuff, contract it out, get an alt, get some friends (as someone else mentioned), or just give it too me!