Only contact pairs can be activated and deactivated using *MODEL CHANGE. For general contact in Abaqus/Standard you can use contact inclusions and exclusions to activate and deactivate selected interactions. In Abaqus/Explicit you can use *CONTACT, OP=MOD/NEW to modify/respecify general contact definition (again using inclusions and exclusions to control general contact domain in each step).
Thank you for the detailed explanations.
I am now thinking of running step i without said contacts and then in i+1, importing the model into another run, and declaring the contacts with the imported sets.
I think this should work.