Well, it was a challenge. Especially not being able to use trains very much kinda made it hard in the beginning. First thing I did was buy two planes and then left the computer running for about ten years. After than I had some money to build ships, bus stations (some buses had negative income due to the cities being so small), and so on. Then around like 1990 I started optimizing everything. I deleted some road vehicles, built new ones, and even replaced three oil trucks by a train line (bottom of the map). It took a while to get all vehicles to make more profit than € 20,000 a year. Also, I had to further increase the size of the cities in order to be able to build more stations. When I finally reached 80 stations I built some more RVs and ships. Trains don't make much sense with a weight multiplier of x15 (the one coal line that I have profited from the height of the coal mine compared to the height of the power station).
Altogether I'd say it was quite a challenge to optimize things at the end but the beginning was a little... boring? Maybe even annoying because of the few industries that existed at the beginning (I funded two forests later on). As you said, the key is expanding the cities. If you don't expand them, you'll never reach the 80 stations, 120 vehicles, and minimum income of 20k...
But yeah, it was a bit of a pain in the neck in the beginning. I tried trains first, then restarted the game and tried RVs (they didn't make too much profit) and then started with planes. It's lame but it pays. I wouldn't do it again because you only have stuff to do every few years (building a new bus stop and maybe two buses) and the rest of the time you get bored because nothing really happens and no new industries are funded due to the height of the terrain.
However, I must say, I was motivated to do it and got real happy when I noticed I was close.
p.s. We should play a MP game together in coop mode, that would be one hell of a company
EDIT: BTW, I set breakdowns to zero mostly because I hate the sound of it (like the whole train is falling apart) but also because trains are very slow already (weight multiplier x15). I don't think it would have made THAT much of a difference since most of my income was based on planes anyways. Also, I did use station walking (meaning unused tiles) but only because the land was very hilly... I could have changed it later on I guess but I didn't...
Make love instead of war! Poppen statt kloppen!