Mendix doesn't have a feature to make the domain model of your own module read-only. You could post this as an idea on the Idea forum. If Mendix thinks it's a good idea too, it might be introduced in a future Mendix version.
Hi Ankit Gupta,
We can’t edit or add attributes or entities in the System module’s domain model. But we can give cross module association to the System module entities. I think, we can’t restrict other team members to access the domain model. Its common for all. If you want to access the domain model yourself, you should work alone instead of working with Team members. ;)