I was under the impression (havent looked it up or anything) that what makes BB and CC creams work is that they sit on top of the skin and have a light airy feel.
You aren't going to be able to achieve that with natural oils unless you add some silicones into the mix. They help to create that dryer feeling that doesn't feel heavy. I would probably guess most have dimethicone and other silicones.
I went ahead and looked it up:
Here are the ingredients from Tarte (most of the ones I've looked up are silicone based like this):
Cyclopentasiloxane, Isododecane, Polysilicone-11, Mica, Polymethylsilsesquioxane, Hexyl Laurate, PEG-10 Dimethicone, Polyglyceryl-4 Isostearate, Stearic Acid, Cetyl PEG/PPG-10/1 Dimethicone, Alumina, Triethoxycaprylylsilane, Dipalmitoyl Hydroxyproline, Diamond Powder, Iron Oxides
Bare minerals doesnt have silicones though (then again, they also don't call it a BB/CC cream):
Water, Coconut Alkanes, Propanediol, Squalane, Trehalose, Isostearic Acid, Glycerin, Silica, Agar, Caprylic/Capric Triglyceride, Globularia Cordifolia Callus Culture Extract, Salicornia Herbacea Extract, Melilotus Officinalis Extract, Coco-Caprylate/Caprate, Butylene Glycol, Lauroyl Lysine, Sodium Hyaluronate, Succinoglycan, Polysorbate 60, Cellulose Gum, Polyglyceryl-4 Laurate/Succinate, Sorbitan Sesquiisostearate, Magnesium Stearate, Magnesium Hydroxide, Magnesium Chloride, Potassium Chloride, Calcium Chloride, Potassium Sorbate, Phenoxyethanol. May Contain: Titanium Dioxide, Iron Oxides.