This is a function already available in Rappatools script collection which has become essential to my workflow.
The default attach/detach objects function takes too many steps in my opinion:
1)Select an object
2)Convert to editable poly/mesh
3)click on the attach button or list icon
4)select the other objects you need to attach one by one or through the object browser etc.
With Rappatools you can select any number of objects irrespective of the object type and click on the "one object" button which automatically attaches them in one editable poly object so basically condesing 4 steps into one.
Inversely by CTRL+clicking on the same button you can "explode" an object to elements.
I would love to see this implemented in the core 3ds Max UI as I believe it will save every user tons of time and speed up productivity.