I usually keep my officers' names and appearance but I replace them as I get new officers. When I get a new officer that's blue or purple and is also the same sex and species as one of my original Boffs I head to a tailor and go the first customize screen for the original and Save. Then I take everything off the officer, delete them, and have the new officer Join. Then when you get to customize, just click Load and find the right one if you have multiple. then change their name and now you've still got the same Boff, but it's upgraded. (replaced by an evil/genetically enhanced clone! Oh noes!)
This is what I do as well.
And in one case in particular (my Vorta/Vulcan hybrid) they actually are evil genetically enhanced clones... of him. His whole crew is actually.