Start with revenue and costs if they are the real economic drivers, but tailor the sub-branches to the situation. Revenue could mean price, volume, mix, customer segment, channel, or geography depending on the case.

The structure becomes less generic when each branch reflects the client's business model and the reason profitability may have changed.

You do not need unusual top-level buckets just to sound creative. Good tailoring usually happens inside a simple logical structure. If useful, this guide on case structure vs. case framework gives more detail.