It might depend on the firm. I think there are any number of things you could go for, and the question can show both commercial awareness and wider legal knowledge.
For example, GenAI is very controversial with issues like the "Studio Ghibli image generator", and here the government has made statements about its plans, so for this you could look at how other countries are managing AI and where the balance might be between protecting creative industries and enabling tech.
Similarly you could look to solve problems in society, e.g., https://www.macfarlanes.com/what-we...veroo-drivers-not-workers-says-supreme-court/ the SC decided Deliveroo drivers are not workers, which means that Deliveroo (et al) are not responsible for illegal immigration offences and don't have to provide employment benefits to staff. A law could change this.
You could talk about proposed legislation too - for example there is the Planning and Infrastructure Bill, which imo is not a new law, but a whole raft of them, but in that context you could propose a specific planning reform that are not in the bill, but has been suggested by others, on the basis that your particular law would enable more economic growth/housing/whatever.
If you look at the Law Commission and others, there are proposals for law reform that are made and perhaps you think are great, but haven't been implemented, and you could look at those.
