craftgrrl | soap-additive question

I am planning on making soaps for the holidays and haven't done it before, and I have a question for anyone who has--

I read in the FAQ that someone used Dr. Bronner's peppermint liquid soap in their glycerin soap to add scent. Along those lines, would it work to take some granulated body scrub and use it as a soap additive? I'm thinking it would provide color, scent, plus those nifty little scrubbing grains, if i just swirled/ mixed it into my soap base? Or does anyone know if combining a pre-made bath product with soap base would create some sort of problem?

thank you for your help!

edited to add: what about other pre-made products, such as a touch of lotion, skin toner, etc? would the additives in these products mess up my soap? thanks!