I would start with the parts that have perhaps the widest appeal (e.g. fonts, code marketplace) and work your way back to an editor. The problem with editors i

I would start with the parts that have perhaps the widest appeal (e.g. fonts, code marketplace) and work your way back to an editor. The problem with editors is that they have to compete not only on basic features, but compete with every plug-in that ever existed for existing text editors. And on top of that, server-side storage can be a deal breaker (e.g. hobby projects, who won't pay you, may put up with it, but a business would want to keep its own copies of things). If you can think of a way to package up the server, e.g. so a business could buy the whole thing and run it behind the firewall on their local stuff, you'll be in good shape.