Beware that the Interactive Diagram superficially might not seem to care much what you use for piece IDs, but that it could wreck some of its functionality when you do not use single-letter IDs that are all different. E.g. promoChoice is not able to distinguish pieces that have the same ID, and morph and captureMatrix don't understand multi-character IDs. There might also be an issue with the ability to read back its own games.
Beware that the Interactive Diagram superficially might not seem to care much what you use for piece IDs, but that it could wreck some of its functionality when you do not use single-letter IDs that are all different. E.g. promoChoice is not able to distinguish pieces that have the same ID, and morph and captureMatrix don't understand multi-character IDs. There might also be an issue with the ability to read back its own games.