That looks like the right approach to add new inheritance to the end of the list for an upgrade. This would cause the storage variables for those newly inherited contracts to use storage slots that are after all of the other existing inherited contracts' storage slots.
One thing to keep in mind is that adding an inherited contract, even at the end of the list, would cause the storage slots of your actual contract to be shifted as well. Possible solutions are to use storage gaps or keep all storage in inherited contracts only (see this thread). If you are just using the Wizard and do not use storage variables in your contract itself, then this is not a problem.