Hi,
We should be very careful with aet field deletion.
I think these structures are relevant to BI system, are you sure only these structures are having this field? you can remove the field from these structure but make sure that should not disturb other fields.
If you want to create the field again then check in TR as well. Actually when you delete the aet field, system will not set delete flag for the object in TR. While doing transport system may give some errors. Careful with the TR as well.
Best Regards,
Dharmakasi.