DIsclosure: I am using AC24. If this has already been addressed in AC25 then consider this solved.
When deleting layers containing objects in a Teamwork there is a warning that deleting the layer will result in deleted elements / missing attributes. If the user opts to move those objects into another layer those objects will still have "missing" layer attributes because they were not reserved. The user has to reserve the entire project to avoid this.
Deleting layers should prompt a dialogue to reserve all those relevant objects and be able to handle any requests. As long as those requests aren't granted there should be a warning sign that "unreserved elements will have missing layer attributes" or something similar.