They need to be converted to the new parts system, which is a lot of work and very time consuming, before they can be decorated. Eventually you will be able to decorate them, but it might take a while, since there are a lot of parts to be converted.

is there a way we can get clone helmets prioritized on getting added

Well you can ask for a UV map of the part to be added in Official LEGO® Sets and Parts or scroll down to the bottom of the page an press Contact Us.

There is already a UV map for the part, just not a configuration, which is what is needed for it to have custom decorations.

That is what I meant.