Refreshing dynamically the characteristic dropdowns based on the other characteristics being selected is quite complex. We don't plan on ading that any time soon.
If you have two characteristics for your products, you can use a "table" characteristlic display method and it will display a 2d table of the characteristic combinations and only the published ones will be selectable. And you also have the option to directly display a listing of all the variants on the product page. And even if you use the dropdown/radio button display methods, when you select a variant which doesn't exist, you won't be able to purchase it.
so even though it's not exactly what you want, you can already have alternative solutions quite close to what you want.
And if you really need to have that rapidly on your end, you always have to possibility to override the display of the characteristics as explain in the developer documentation:
www.hikashop.com/support/documentation/6...r-documentation.html
