My sales advisor informed me that this can be done since that's what we ended up with my M3 that I just ordered a few days ago. I haven't seen the switch to the new order yet but he did tell me to cancel the previous one and he would submit a goodwill request to switch it over.
I believe this is not true. If you look at your account, you will see the Order Fee is part of the total Car Price (a long with Destination and Documentation Fees). Then, below, there will be a credit for the Order Fee, but that is only because you had to pay it to make an order. The Order Fee is just an additional component of the purchase price.
I had a conversation with my SA on 9/5 about changing colors of my M3 and asked about changing deposit to MY. They said they cannot do that anymore and if I wanted to "change" to an MY, I would have to go through the ordering process again and the M3 order would still be active