Mordric, the possibility of minor mutations is a great idea! The Ximni are rugged, so any mutations you see will be rugged. A Ximni with non-rugged mutations would hide them. For example:
A Ximni who grew horns would enhance them, polish them, make them stand out.
Whereas a Ximni whose mutation was antennae shaped like petunias might have them surgically removed and replaced by artificial horns.
A Ximni whose mutation was a voice like Beezabub would scream and shot every chance she/he got.
A Ximni whose mutation was a body odor like lilacs would be embarrassed and cover it over with a musky deodorant. This goes for male or female Ximni.
A Ximni with red eyeballs might were makeup to enhance them.
A Ximni (male or female) whose mutation was pink hair would prefer to shave it off and go through life bald.
A Ximni with bad-ass spikes down his/her spine (like a dinosaur) would paint them, sharpen them, and/or chrome plate them for the whole world to see, at least above the shoulder blade.
The further I go the better I like this. So let's say about 10%-15% of Ximni have a visible mutation. That means many ships will have one bridge officer with a bad-ass looking mutation. I'll talk to my makeup prosthetics guy about manufacturing some of these for players to wear.
"Damn the torpedoes! Four bells, Captain Drayton!"
(Likely actual words of Admiral David Farragut, USN, at the battle of Mobile Bay. Four bells was the signal for the engine room to make full steam ahead).