There is no OSM2FS2. Just my poor fantasy.
Well, then I guess you have your answer... there is no single source with all information inside for a single tool to automatically make a consistent scenery, or you get a rather average result.
Making a good scenery means picking data from various sources and mixing them wisely. There's some preparation work before to prepare and filter the data, and this isn't automated.
What can be automated is afterwards the conversion toward AFS2 format, which is the aim of a tool like ScenProc.
I initially started working on an alternate, AFS2-specific tool, but quickly found out it didn't make sense reinventing the wheel since ScenProc exists. It will be easier to integrate AFS2 needs to ScenProc...