Custom RSS feed based on custom field and author

This is a kind of strange request, but I’d like to put it out there and see if anyone knows how to handle it.

The blog I’m setting up has a lot of authors (dozens), so I’d like an RSS feed for each of them. This function is provided nicely with Chris J. Davis’s hack to have Author RSS feeds.

However, within the author, I’d like to provide a different feed for all posts with the same custom field.

To be clear, it might look something like this:

https://www.mydomain.com/author/customfieldsanitized

or

https://www.mydomain.com/author?customfield=sanitizedname

I hope I’ve done a good enough job explaining this. I’d love to work with someone on this – or if anyone knows the general concept I could do it myself.

If needed, I could pay for someone’s services to help me out with this.

Thanks.