Erik Jurrien Menzel
The only thing I worry about is the more formal you make it the more you risk planting the idea that having a black belt is realy realy important.
When I was practicing judo we had a ritual to keep the recently promoted humble. After the certificate/belt had been presented the newly promoted person would be thrown by everyone in the dojo. They would start with the highest ranked person present and work their way down the line and each person was allowed to use a favorite technique.
I think that ten years or so from now when I finally can teach Aikido I'll include the practice.