How's your maths? Here's something I'd pay quite a lot for: intelligent inventory optimisation in an easy to use SaaS format. Quite mathematically intensive to do well, so most SMEs don't have the skills, but directly saves money so has a clear value proposition. Some pointers for an MVP I think might be sensible: Model stock arrival and product ordering as Poisson point process with probability based on recent data…
There seems to be a lot of competition in this field. Did you evaluate existing services? It's an interesting problem.
For a small ecommerce retailer, you don't want much like that; maybe I've missed it but there seems to be a gap for the Basecamp of this niche. A shopify plugin might be a good way to get standardised i/o rather than adapting to proprietary systems