There should be a possibility to add solutions from any category to FAQs. This helps to keep changing the FAQ without disturbing the categories.
Something like this
In fact there should also be an ability to add a solution from a response in the ticket.
Posting solutions in FAQ and any other category is right now not in the roadmap. You would have to manually copy and paste the content once.
And adding solution from a response in a ticket is actually available in Freshservice. :)
While replying to tickets, you can add email@example.com in CC and it would show up in draft.
Hope this helps!