To restore them to default values, I believe you would have to store their default values first. Example location would be on Construction, since that is first and foremost, even before Event Begin Play. Store the defaults of things you want to be restored to default. Set them to those values when you need them put back to default.
Another way to get defaulted values to come back is to spawn another instance of the blueprint. It will have the default values loaded in. May not be the best ways of doing things, but at least you have two options now.