During the 1970s especially, it was not unusual for a handful of members of the Legion of Super Heroes to guest star in books in the 20th century (Justice League of America, Brave And The Bold, DC Comics Presents, Superman, etc...)
The guests from LSH usually consisted of 7 or 8 members. So, pick 7 or 8 of your favorite Legionnaires to guest star in a 21st century book. Name the book and even give a plot-line if you like.