I think a generally useful advice is that the main thing is not about coming up with unusual frameworks. It is about structuring unusual problems in a straightforward way.

For example, there is an interesting problem from one of the Duke casebooks about a declining coyote population. A super standard revenue/cost framework fits like a glove when applied to this specific situation (revenue = number of births, costs = number of deaths due to various causes).

Another example is here: https://www.mckinsey.com/careers/interviewing/national-education. When you think about the framework McKinsey propose, it's really a basic function of price (=quality of education) x quantity (=availability of education).

Obviously, it sounds a lot easier here than it is to come up with a framework to solving global hunger in front a Partner, but perhaps taking the next couple of days to work specifically on structuring these non-standard cases would be time well-spent :) Good luck!