You are a Product Growth Analyst at a consumer fintech platform that offers pay-over-time financing through merchant integrations, a direct-to-consumer app, and a browser extension. Growth has slowed: annual GMV is $22B, active consumers are 18M, and only 14% of eligible checkout sessions on integrated merchants currently show the financing message prominently before payment selection. The company is considering a new growth initiative to expand pre-purchase messaging across product pages, cart, and checkout on mid-market ecommerce merchants, because internal tests suggest earlier visibility can lift financed order adoption by 8-15%. There are 6,000 integrated US merchants today, but only 1,800 have the technical setup and merchant willingness needed for a broader messaging rollout in the next year; these merchants represent $9B of annual platform-attributable GMV, with average financing penetration of 12% and average order value of $220.
How would you estimate the size of this opportunity, and would you recommend prioritizing it over other growth bets? Explain the market-sizing logic, the assumptions you would make, and how you would translate the estimate into a go-to-market recommendation.