It would be useful if view attributes could be passed to individual choice field options in a similar way as attr for most field types. Currently it seems not to be possible without duplicating both ChoiceList PHP class and duplicating both choice_widget and widget_choice_options template blocks.

If the core form module supported (arbitrary) attrs in choice options, it would allow easy extension of the core choice field type for custom types. Custom data could be passed to the template, allowing HTML like:

<select name="search_engine_selection">
    <option value="google" data-url="google_logo.gif">Google</option>
    <option value="bing" data-url="bing_logo.gif">Bing</option>
</select>

In my example, data-url would have been passed as an attribute to each option.