"Dynamic," / "Live," Objects

First off: sorry if this is already suggested. I searched around a bit, but as I was just making up names for it I didn't know quite what to search for. It seems like something that would have been suggested already, so if it is tell me and I will delete this.

Proposal: Something I would like to see more of is "Dynamic," or "Live," objects for lack of a better term. Something like what 3ds max has, where a Sphere or a Cylinder has it's parameters exposed permanently after it has been added or until it's converted to a mesh.

While it would only be a little helpful for things like spheres, it would open up the doors for more complex objects which are difficult to change after the fact such as stairs, trees, or anything else procedural.

It would also be helpful in boolean CAD workflows as it could provide 2 important features: 1) It would allow easy resizing of complex shapes after the fact; 2) Different resolutions could be set for "Render / Export," and "Preview," similar to how the subsurface modifier works.

We already have the distinction between meshes and existing forms of "Live Objects," such as curves, nurbs, metaballs, etc. It would just be good to have more of them, or better yet a better way to add your own through python scripts.