There are clearly political considerations and they must not be solely technical. In fact, it is important to know how lawmakers can show their political sovereignty, meaning what matters they are able to decide.
All your concerns are complex ones and they could be seminar topics. But I would like to go back to one very specific point. I keep thinking of the words of Jean de Maillard, a sitting French judge who writes about these issues. He says that we are in a situation very much like the one you mentioned, drug trafficking. These are the words of a judge. He feels that the law these days is used by multinationals to knock everyone who does not play by their rules out of the competition. In a way, we are using the law to make our citizens and our SMEs pay a significant amount of tax while the multinationals get all the latitude they want offshore in taking advantage of very favourable systems. This is a problem.
How do we solve it? Jean de Maillard himself is conflicted by this historical contradiction of ours, which does not fit with his thinking. He feels that we could do away with tax havens with the stroke of a pen. They are British or American dependencies. Canada has agreements with them. At the same time, it seems that the players who have a lot to gain from tax havens have a very strong hold over lawmakers, who always need fancy footwork to keep watch over interests that are by no means clearly defined.