I've used multiple web development programs over the years from Front Page, to Adobe GoLive and Dreamweaver, to Hype, and Panic's CODA (https://panic.com/coda/). CODA is a fantastic development program that we use for our University website(s) (https://www.an.edu). The websites we develop are very complex with multiple Apps like an Applicant Process system for online and international students, a news content management system, a webinar sign-up, register, view, and archive system, etc.
We use Lasso (http://www.lassosoft.com) as the scripting/middleware product to do the dynamic work using a SQL database.
It's been very difficult to build visually high-end, responsive, websites so we typically farm out the design and HTML/CSS to use as a template. If WebFlow were allowed to integrate into development programs like CODA, it would blow every other web development program out of the water.
CODA has been very strong on the coding aspect with great FTP publishing features and scripting language support but completely lacking in WYSIWYG visual design. Maybe the two you could meet?
WebFlow can be so much more than a "simple" website builder->hosting solution but rather the pinnacle of responsive web design that other mainstream development tools could integrate into their application. Keep what you have here for the Mom & Pop websites but pursue what I'm saying above to open your product up to a broader and more professional customer base.