CT Spec Trading
By the rules, the limiting factors are as you have said. I have, over and over, taken a type S and just hung out waiting for the rigth cargo. On the right run, and the right cargos, using brokers, about one cargo that makes about a 5- to 8-fold return can be traded about every two or three months. In a year, the seed money has increased about a thousand fold at least.
The first couple cargos can be run in the Type S to save seed money, and keep operational security. After that, space is just booked; when the cargo has a base price of 10MCr or so, then the carrying ship is chartered, and no passengers carried, to decrease hyjacking exposure.
If the run is between A & B ports, then there is no piracy risk, per the tables. Now as a ref, if one sticks to the same route, carrying cargos of several MCr, it should attract pirates, so that routes will have to be changed every few iterations. (Usually, this requires just finding a Ni world with an A or B starport).
The CT tables make it just a matter of seed money, a good route, and patience. I add security to the mix as a ref. I can imagine adding corrupt officials, corrupt sellers, and cargos that are not on the tables. I have not used the Merchant Prince tables, because I am lazy and they hurt my head. My feeling is that they would make finding the right routes and cargos more difficult, and change the math a bit, but not the strategy and other variables.