So you're saying that the exchange has built-in mechanisms to automatically liquidate positions and prevent a cash deficit? I've encountered some less diligent brokerages that seem to not follow this practice, leaving their clients vulnerable to holding positions with resulting cash losses.
In those cases, if there is in fact a cash deficit after the firm closes the position (assuming the brokerage is sloppy), would they then liquidate the options on futures position to generate cash to cover the shortfall?
name the broker, i don't believe any regulated futures broker would be that stupid.