And with canon characters, thereís really no sense of tension when theyíre placed in danger. Iím reasonably sure that Captain Kirk, or Commander Riker, or Major Kira arenít going to be killed during the course of a story. With original characters, the author is free to do whatever he/she pleases with characters of their own making, and very little (if anything) is out of bounds.
Hello - it's fanfic
. You can kill off the Captain or Riker, or Kira if you want. You can take the characters off in totally new directions.
One series I read a long time back had Spock marrying a Human/Vulcan woman named T'Marse (she was a navigator on the Enterprise). Pon farr happened, T'Marse got pregnant, and Spock decided to resign from Starfleet. He and T'Marse put together a private scientific research vessel that included a couple of other scientist couples with their families, and went independent.