Like it or not it was the ethical and probably the legal responsibility of Coinbase to be prepared for this type of event, not to mention there was significant warning in advance of the split. One way to protect Coinbase is to show some significant goodwill. Simply guarantee no loss of value of BCC on your access date. You can probably buy insurance against the risk if you wanted to. Offer an equivalent amount of BCC at it highest price between the split date and release date to each of your customers. If you wanted to reduce Coinbase’s risk and liability further offer each of your customers a choice to have the value at the time of the split or the value as of the release date. They would make that choice now though an electronic signature. The faster that release date arrives the lower your risk. This also puts some control back in your customers hands and will help to mitigate some of your potential losses along with the desire to sue Coinbase. The goodwill should go along way when the lawsuits come and I can not imagine that a judge would not look favorably upon these attempts to mitigate customers losses.