I believe the elements were intended to be used on a circlet. So why not put them back on a circlet base? The lower part was intended to hold a large stone (Koh I Noor?) but why not use the large aquamarine from her necklace/tiara. That central element might be replaced by a new element, maybe a version of the sapphire brooch of Prince Albert so she has a sapphire tiara to go with her Demi-parure. If the central element became interchangeable like the Gloucester tiara Sophie could alter it from event to event.

She would need a serious set of aquamarines to go with the new circlet though.

I'd rather see her swap the piece for the Russian sapphire bandeau or Queen Mary's diamond bandeau. That central element can be taken out and so something else could go in it's place.