Re: If Mt.Gox opens litecoin trading, could that suddenly eliminate the $15+ spread?

What you are missing is that the spread is not due to the relative value of the Bitcoins, it's due to the relative value of the $.

or lack of value of GoxUSD as it cost 20% to withdraw.

That would pump the Gox valuation of litecoin at the expense of its bitcoin valuation. That would be very bullish for litecoin.

The LTC value @ gox would just end up being 20% higher than everywhere else as well. IT's a Fiat IN/Fiat OUT problem.

We agree, but for the "just" characterization.