This is a good approach for the most part, but it's limited (more on that later). In regards to incorporating this into the framework, you need to make it specific to the prompt. Clarifying questions come in really handy here, because you can gauge from what angle to tackle this part(based on industry, objective, etc.).
What I mean is, if you've been told about a clothing company that sells pants, shoes, and shirts, well, it's pretty clear you should break down this problem by product mix, and articulate what products. If you're not told the mix, but it's clear this is a product mix question, then hypothesize/customize in your framework! i.e. "I'd like to look at this by product mix, i.e. pants, shirts, shoes, to see..."
However, your approach is limited for a few reasons:
1) When looking at product mix, you should look at customer segments within the product mix. So "Is X product unprofitable? Is this because of high costs, or are we over/under priced. Importantly, are we targeting the right demographic with our pricing, advertising, placement, etc"
2) There are more segments than just customer and product - if you think this way you will miss the point on different cases
a) If you have a company that sells commodities (can be an oil company, or maybe a better reference is a nickle mine), well, all of a sudden neither customer nor product mix work do they? In this case, you need to look at commodity prices/trends, and focus on the costs along the value chain. For example. if we're oil and gas, you're probably not looking at customer segments. It might be product mix, but only if you've got a vertically integrated company that sells products upstream, midstream, and downstream (i.e. crude, LNG, petrochemicals, etc). If not, it could be purely a cost-out problem
b) If we're a multi-national company, or a franchise, well, maybe our issues are geographical. If you're a US-wide burger chain, you'd probably want to segment by East Coast, Midwest, South, etc.
There are other examples, but i think you get the point. In summary: Tailor your framework to the prompt: industry, situation, objective, etc.