I'm puttering around with a new race, along the line of ye olde flesh eating ghouls. Does anybody have a little advice on how I could manage to attach the cannibalism capability from the Ring of Namira to a race, as a natural capability?

You'd need to create a custom spell effect with a script resembling this:

Scriptname CustomCannibalism extends ActiveMagicEffect Event OnEffectStart(Actor Target, Actor Caster)   Game.GetPlayer().AddPerk(DA11Cannibalism)endEvent

Then create a custom spell (Copying another Race's "Blood" ability would be easiest) and attach your custom magic effect onto it. Then attach that spell to your race as an ability.