It's in our plans to add more scaffolding parts like the ones you mentioned, but we can not promise you a date just yet.
Regarding the "Adjustable Columns foots", you may find it (Name: Scaffolding Base) in the latest library version under the Scaffolding Parts category.
Do note that this part is snapped at its full height, but you may then move it up and down at will. On top of that, once you use the Break tool on this object, the clamp can also be moved freely to the desired height.