Figuring out app for my friend's ecommerce business idea

My friend wants to build an app which will put all the city's small retailers online. Trying to give a tough competition to the likes of Zepto and Blinkit, while at the same time being a Knight in the Shining Armour for the smaller retail players in small towns, protecting them against the onslaught of well-funded ecommerce startups (with a different delivery model of operating through dark-stores). We are figuring out the right app for his vendor onboarding.

How far will we succeed?

#Davids Vs. Goliaths