Does anyone have any advice on how to achieve this?
When exporting elements from one template to another, try exporting the elements underneath the camera rather than the cameras themselves. Then, in the target template, import the exported objects underneath the existing camera's in the templates to try and mimic where they were in the template of origin.
Alternatively, instead of exporting / importing from template, I suggest choosing your primary template (e.g. the segmentation template) and then adding new objects via the add new button in the objects panel. For example, to add a new billboard, you can select Add New -> Billboard or to add a new face mask, select Add New -> Face Mask.
Hope that helps!