Map additional domains to individual post categories with unique themes?

Hopefully I can explain this in a simple way. My goal is simple:

1. I want to do all of my posting on a single main site with a single domain
2. I want additional domains to map to post categories, with their own unique themes. This way a second domain would show content for one particular post category, with its own theme. But I would only have to post on the main site domain, and the additional domain would only show the specific posts for its specific category.

For example:

1. I have a main site, e.g. http://www.mysite.com
2. I have post categories, e.g. http://www.mysite.com/fishing
3. I want to map additional domains to the post category URL, e.g. http://www.mysite.com/fishing = http://www.ilovefishing.com
4. This way, the category of "fishing" would only display fishing-related posts, but with it's own unique theme, pinned posts, etc.
5. If there was another category of say hiking, ex. http://www.mysite.com/hiking, that would be mapped to http://www.gohiking.com, again with its own theme & only pulling hiking post-category posts

So two questions:

1. First, is this even possible? Perhaps with WP multi-site?
2. Does GeneratePress support this?

The overall idea is to have a single main site to post to, then custom domains that only show the specific category posts for that domain, with a custom theme. The main site would show all the posts from all the categories, then the additional domains would only show posts from specific post categories, in a custom GP theme for that particular website.

Ideally, this would all be done seamlessly, so I could just post to the main site & it would automatically update any related domains under their own themes for that topic. Not so much interested in sub-domains or sub-directories as much as just specifically mapping additional domains to specific categories. So a single database, but additional domains are filtered & mapped to one specific category, with a custom theme for that domains.

I guess post categories (ex. mysite.com/fishing) could technically be considered a sub-directory (not sub-domain) on the main site. But I'd like to be able to custom the category domain with its own separate theme.