I would argue that "usual motivation" is itself an issue because most lawyers aren't going to be doing work focusing on "overall values and influence in society". They're going to be reviewing and writing contracts and suchlike for companies. I think it's important to be realistic about this - as if you're not actually interested in that, you might find a law degree rather tedious, and you might also not really be that keen on pursuing a legal career. And since you can (and about half of all solicitors do) pursue a legal career with another degree (say, in philosophy and/or politics...) anyway, if your interests are less in the actual substance of a law degree and in those of another area, it makes more sense to look at doing a degree in another area.
The different areas of law covered in a law degree are all still "law" and will require you to read case law and apply them to legal problems and write essays on those as I understand. And my understanding is the majority of those essays are not going to be of the wider ranging philosophical kind, they're going to be focused on specific laws and the legal problems that arise from them. These are distinct from ethical or societal issues that may arise from laws and legislation, I'm inclined to think. Unless you are doing a more socio-legal studies focused module (which would probably be an optional module anyway).
In terms of the structure as a brief segue into something else it's probably ok although likely unnecessary. I would note you should be careful when discussing human rights in this context to focus on the legal aspects of them and not the humanitarian/philosophical/ethical/political/etc aspects so much. And again, if your interests skew more to the latter topics then you might find a degree in e.g. politics, IR, philosophy, humanitarian studies etc, more appealing and aligned with your interests (and would still allow you to pursue a legal career potentially).