Hi there!
I tried a number of page builders and found BB as the best out there! It’s even easier to use compared to Wix! Btw, just a thought. Rather than just editing pages, would you consider doing template builders, or builders capable of editing templates? 
As such, we only can edit landing pages, but we cannot edit how the blog archive or the blog page looks like. Neither can we edit product pages and product archives.
But if you can come up with an editor which can do not just page building, but template editing, that’ll definitely rock!