In Mendix it is very easy to change your Domein Model (Entities / Attributes / Associations). This is one of the perks of Mendix in my opinion. Yet it will come with challenges concerning using OQL / BI / Java actions, since these use specific (Case Sensitive) attributes / entities etc. A lot can be solved with good documentation, and development guidelines. Yet people make mistakes, especially in large development teams.
What i suggest is a possibility to Lock an Entity (name), attribute (name and type), and association (Name and Multiplicity), by simple adding a checkmark on that specific entity / attribute or association that you want to lock. It can allways be unlocked, but for developers it is instandly recognizable that they should not changes this entity / attribute / association, without repercussions.