Punitive measures against transgressors is one issue, but this does not necessary solve the problem of how someone who is blocked in by a transgressor can actually get home!

Agreed, but in some ways I'm more interested in the former problem, because such a transgressor is likely to do so again and again, and helpfully moving their car a short distance when a spot becomes available or paying for it to be towed at your expense only encourages them. I'm not sure 'punitive' is necessarily the right word, since it carries such a strong financial implication, but I do think it would be a good idea if we could strongly discourage people from doing this. It's not how the law is set up, but it wouldn't seem unreasonable to give penalty points on the licence for such behaviour, for example. As to working within the law, I'm not qualified to answer, but given the choice between two lawful alternatives, the one the inconveniences the offender more would be my choice.