How about importing a composition from an Ae file back into After Effects maybe by using dynamic link. The same as smart objects in Ps, or embedded files in Ai, or reference files in 3DsMax.
It will be helpfull in reusing assets and most importantly collaboration between team members working on the same project.
Suggestions for the naming "Smart Comp", "Reference Comp", or "Embedded Comp".
Wouldn't it be a nice feature to add?