The only way to minimize risk totally would be if the charter company would put the money in an escrow account safe from charter companies that may/will go under...and have a refund policy in the event of borders being closed.

Right now the charter companies like many businesses are thinking about a short term cash grab to try and keep afloat...at the long term cost of their reputation among charterers. Personally I wouldn't put new money on the table for a charter until we find a "new normal" but do have a credit I want to use up as soon as possible.

TMM will have a distinct marketing advantage in my mind with a 100% refund policy....

I can tell you from personal experience the credit card companies will not help you at all.