Has anyone ever done budget/forecast at a higher level entity?

I would think you could potentially do this with a linked cube setup, Have one entity dimension setup for the parent cube where worse case you have a Base high level under the parent you are extending from then you would just have the lower level cube for actual and they would do the compare of actual to forecast in the higher level cube.
Entities dont extend like other dimensions so you would need a unique Entity dimension. You could combine them in a Top Level Cube under a common parent to facilitate reporting.
An Entity cant be a parent in Actuals and base in Plan like other dimensions.
The only way for linked cubes is to share the entire entity structure into another
I am thinking if it is a grand structure we may want to make a separate entity dimension altogether. If it is small would we just put the base member in? or use an alternate hierarchy.