Can a script be used to switch between the "internal positioning" and "external separation" states of the image?

Hi — yes, this can be scripted, but there is no single built-in command that flips an image between anchored and free; the two directions need different techniques:

Anchored → free (release): use pageItem.releaseAnchoredObject() — it releases a custom-positioned anchored object and the object stays where it is on the page. One important caveat, confirmed by Community Expert Uwe Laubender in this solved thread: https://community.adobe.com/questions-671/release-all-anchored-objects-at-once-882957 — releaseAnchoredObject() does not work for Inline or Above Line anchored objects; it fails silently, with no error. For those, the reliable workaround is to duplicate() the anchored object, delete the original, and keep the duplicate — it lands as a free object in the same place.

Free → anchored: the scripting DOM has no “anchor this object” method. The scripted equivalent of the manual workflow is to cut the object and paste it at the target insertion point — it comes back as an inline anchored object — then set its anchoredObjectSettings (anchoredPosition = AnchorPosition.ANCHORED for a Custom position, plus the reference points and offsets), or re-apply your object style, which carries the Anchored Object Options. Adobe’s guide to the three position types (Inline / Above Line / Custom) and to releasing an anchor: https://helpx.adobe.com/indesign/desktop/add-graphics-and-media/transform-and-arrange-objects/create-position-anchored-objects.html

Choosing the anchor point (end of the paragraph closest to the top of the image, within 2× the leading, otherwise give up) is custom logic the script has to implement — compare the image’s top edge (geometricBounds) with the paragraphs’ positions in the text frame and pick the nearest one. There is no built-in option for that rule.

So: feasible, but it is a custom script built from those pieces rather than a one-liner.