Regarding Vilnius-Billund - I do not think there exists enough traffic between Lithuania and West Dennmark to warrant such a route. I even would say that the traffic is completely non-existant. I personally never heard of anyone from that part of Dennmark or even met or heard about anyone from Lithuania who said that he went there.
Adding to that Wizz Air were having hard time sustaining a lot more obvious routes like Stockholm or Trondheim so I have my doubts.