When a Model is updated, add an option to only update CI/Assets where the prior data in the Model matches the current CI/Asset. This will avoid overwriting CI/Assets with customized data. It will, however, potentially invalidate CI/Asset data that currently matches the Model
As I understand it, there are currently the options to:
1) Update nothing already in existence
2) Update everything already in existence, without regard to whether the CI/Asset data still matches the Model.
An alternative would be to add a checkbox on each CI/Asset to "Ignore (or Accept) Model updates." This would ignore data pushed from an updated Model except when the Model is ne to the CI/Asset