It would require some very significant reconfiguring of the widget. The problem is going to be getting the information. It is always possible to write an expression that will give you a secondary value if the first value is null (or any other test). The value you are looking for however, is not available to the widget in the first repeater.
The options are not evaluated until the repeater in the popup and so the
loop.options variable cannot be called in the first repeater. The other place that you might be able to get that information is from the command options metadata of an object, but the only way to get metadata into the widget is to add the
fetchMetadata property to a repeater that uses one of the item type sources (e.g., itemsInGroup). Your first repeater uses a user-defined array and so can’t get the metadata associated with any items.