Are there any other changes that have been introduced for MiFID II other than the addition of high precision timestamp fields?
Yes, there are new fields intoduced for the new MiFID data models in support of APA services on-boarding, and new fields supporting extension to existing services but these do not introduce any field types requiring a minimum API revision. Just the upgrade to the minimum field dictionary revision.
This question was first asked in a MiFID IIwebinar (27th of Sep). Please see here: Introduction to MiFID II for Developers