Hi,
Well, the thing is that the radios/dropdowns are actually displayed by Joomla there.
HikaShop only calls the display library from Joomla:
$html = JHTML::_('select.'.$characteristic_display.'list', $this->values, $map, 'class="custom-select" size="1"' . $options, 'value', 'text', (int)$value,$id );
in administrator/components/com_hikashop/types/characteristic.php
And the Joomla display library doesn't set a class for the active element nor does it have an option to be able to do that.
So we would have to switch to displaying the HTML ourselves there.
Possible, but it's more complex than just an if.
And it's the same with have a span around the text.
I've noted that on our todo list for now.