Loyal Sequels-Character References

In sequels, I love when filmmakers have the co-stars return or at least make reference to previous characters in the the previous movies. In Sniper 2, Tom Berenger makes reference to Billy Zane's character Miller. In Sniper 3, Tom Berenger makes reference to Linden Ashby's character McKenna. I think thats so awesome. If they make a 4th film, I'd love to see Billy Zane and/or Linden Ashby back. Who do you think should be back in the 4th film? And did I miss any character references in Sniper 2 or 3 to any previous characters?