Sorry to say I wouldn't call it a true lease if you have to buy it out in one form or another. A "leased" car is turned back to the dealer at termination with either no charge or a disposition fee of a few hunge. There is almost always an option to buy but it is only an option. As a retired dealer rep, I would not recommend either buying out a leased car or putting down much money. "Down" money does not give you any equity, whatsoever. It is nothing more than buying down the monthly payment. Better to keep the cash and pay the higher monthly payment. If at all possible, stay away from balloon payments after 36 months...no one can predict what their situation will be in three years.
When a manufacturer does not offer a lease, it means they don't want the car back. In the case of the C7, that's a dicotomy since the now published residual is pretty darn high. That means ALG or whomever is establishing a residual thinks alot of the resale value of the car...just as with BMWs, Mercedes, Acuras, etc. Sooooo, although the residual established by third parties, such as ALG, may be high, it does not agree with the manufacturers marketing plan or forecast of resale value.
If anyone wants more info, I'll be happy to help. I'm travelling right now and have limited online access until mid-week next.