I don’t think .mogrt’s can trigger scripts yet ? So you cannot give the premiere user dynamicly populated dropdowns without having them run a script inbetween selections.
If it’s just the look of an effect, then could it suffice to just offer placeholder-text like “Option 1″,”Option 2” ?
Or is it setting text-options ? More like select a country first, then select a state/region from that country ?
BTW, the result of a dropdown menu will always just be an index, so even if a script changed the label of allt he options, an expression will not know the new values, only the number of the selected option, and the expression would have to do all the logic the script does too, just to know what actually is selected.