You can change mesh thickness without having to modify the part in your CAD system and then re-import the part.
The recommended option to change the thickness on DD mesh is to use
Offset tool.
Another option would be to:
Note: Editing the mesh thickness property should be performed when only a fill or Fill+Pack analysis is required. The analysis accuracy will be compromised if a Cool analysis is run anywhere in the sequence.
Tip: You only need to select a single entity, then select the check box that will apply changes to all entities that share the properties of the selected entity.