I think skipping belts should be done on a case by case accesment.If i had say, studied Shotokan karate and had a 1st dan,i know all the kata and all other requirements.I then walk into a Goju Ryu school,i do not know one Goju kata,any of the bunkai etc,how could i expect to hold my rank. It may take 1-2 years to learn all of the new kata etc,so i dont think you should be graded to your old rank until then,however i think you should be able to skip grades because of previous training.