I'd like to create a character with custom Abilities and Attributes without causing integration problems with the rest of the game. Optimaly, I would copy the Breton race, and the game would react to the character as if they were Breton (i.e. interactions with NPCs and all graphic interactions). How do I go about doing this without modifying the Attributes for all Bretons?

I tried to copy the Breton race and make my changes on the copied element but I end up with a floating head for a character and suspect that there will be problems later in the game with Vampire transformations, NPC interactions, etc... Help please.

There is actually a tutorial for this if you haven't figured it out already.
http://www.creationkit.com/Tutorial_Creating_a_Playable_Race
You could then copy whatever Abilities and add the custom version under the race screen.