It is does not hard, If you code is correctly written as per Unicode standards. However, If there is any function module/Method to update those, you can suggest them to use that. Else, they can have direct update statement. but, before doing that, they have to have locking Mechanism. They should not just write update statement.
As per my knowledge below are the Cons:
It might not capture the logs by having direct update statement.
If there is any Parallel update happens, there might be a chance for ABAP Runtime error.