I like the direction we're heading with this. This change is long overdue, but i'm still happy to see it happen. so why invent a new mechanism for defining what files belong to which assembly (C# project files) and the dependencies between these assemblies (C# solution files) ?? The easiest way would've been to allow us to specify our own solution. Unity would compile that solution when returning to the editor from another window. Solutions and C# projects already have the nice property of knowing whether they should recompile or not, so everything you're offering here should still work. Seems like a cumbersome solution that already exists to this problem.