If I can ask a question, Will, why would you want a user to be able to control the hashtag on your site? Hashtags are the equivalent to what keywords and tags have been used in CMS sites for many years.

Here's a good example why its not a good idea. As a keyword/tag/hashtag they are used for all users to quickly find relevant content related to the specific word/phrase.

If you allow one "creator" the ability to own and control it then, by design, you preclude anyone else from ever adding content to the keyword.

Imagine if I as a user was the first to create the channel/hashtag/keyword "BITCOIN" or "PEPSI" or "AMERICA" and was now the only user who could add content using that word. It doesn't make sense.

Now maybe I'm misunderstanding your intent. If you don't want anyone, except say a certain membership level, to be able to directly add posts, or edit some things, then thats simply resolved by changing the settings in the "Visible For" settings on the page block (see attached). By doing this you can let memberships like administrative or moderators manage the content without precluding your main users from creating content. Again, unless I'm missing your intended goals.