Is a SaaS for Agencies to create Onlineshops and Product-Websites ...driven by API or GUI - a good Idea?

I like to hear your opinion to our (me and my co-founder) idea.

The Idea

An SaaS Service where Agencies and Developers (following named A&D) can easily create Onlineshops and Product-Websites for their customers.

The online shop and Produktwebsites are HighPerformance WebApps (PWA's), which are created with SEO, performance and easy-to-use in mind.

The A&D are able to create own Templates for layout/design and pre-configuration (e.g Tax or shipping-settings...).

Those templates can be used to setup the whole shop and website automated (and programmatically) by api-calls, or via mouse-clicks in a dashboard (WebGUI).

The Idea behind is, that A&D can save much time, because they don't need to care about setup or maintenance of Hosting, Mailservice or Domains, they can focus on creating a perfect Onlineshop or Product page based on the software we provide.

They also might build multiple layouts/designs for the product websites and online shops to grow their own portfolio of individual designs.

But anyway A&D can build own additional Services around the Onlineshop or Product page the created for their customers (based on our Service). And they can charge they're customers as they like... monthly, per project or anything else.

Our SaaS could be provided as whitelabled solution, or based on revenue by an provisioning model.

We still have a modular api-based shop, and work hard on the dashboard... but initially it was planned for single customers.

What do you think?

What do you think about the idea to set more focus to agencies and developer's... and give them the option to preset and pre-design shops for their audience, without taking care of server-maintenence, Domain-Registration and so on?

Love to see your comments down below.