This is a larger undertaking compared to JDK-8154216 (selectedItems), because far more custom changes are fired on the selectedIndices list. I did some very early exploration but have run out of time (and realised this was going to be a rabbit hole to fully resolve), so I am attaching the exploration code as a patch here.
            
- relates to
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                    JDK-8154215 Simplify selection model code by removing use of ReadOnlyUnbackedObservableList -           
- Open
 
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