At the moment org-element-adopt-elements always appends the new elements after the elements original children. In many cases one might want to append before the original children.
I want to propose adding an argument to org-element-adopt-elements that defines if the elements should be added before or after the children, i.e.
(if append-before
(nconc children (org-element-contents parent))
(nconc (org-element-contents parent) children))
Would this be okay?