OP,
This sounds like a great opportunity. Let's ignore the legality issues and red tape for a minute, and just think about the original question. You have 1 tap available at the restaurant, and what should you have it pour?
Normally, I would say that your idea of an American Amber is a great choice. However, I see it as more or a hurdle than a benefit that Dead Guy is the restaurant's best seller. How many people really understand that Dead Guy started out as a Maibock, and was slowly changed to it's own unique, American Strong Ale and brewed with a propriatary strain? A fan of craft beer knows it is a great beer, but I would be shocked if they could really explain its unique style.
Even people who like craft beer would typically fall back and describe Red Guy as a good, red ale. The bulk of the population either likes a "red" beer, or they don't. Browse the BJCP guide, and you will probably find 15 beers that can be described as "red". Red really means nothing. The problem is that you are going to get constant comparisons to Dead Guy; either "this is better than Dead Guy", or "this is not as good as Dead Guy". The average person/patron does not recognize 80 (or so) beer styles. Spend a few minutes at the bar of your local brew pub, and listen to bartenders/waiters (even the brewer) struggle to explain their beers to curious customers. Even beer-educated employees do not have much to work with if the customer base does not know classic examples of a style. The stretches they make are unreal. I have heard of Bavarian Weizens described as "like Blue Moon", and Irish Reds that are "Like Sam Adams". Color does not equal style. My point is, your recipe might be a great American Amber, but if people are set up to expect one flavor, but they get another, they are going to critique (even if they like what they taste).
I suggest looking at the menu, and choosing a beer that pairs great with food, and is still good on its own. My suggestion is a flavorful, unrestrained American Brown. Give it plenty of body, plenty of sweetness, lots of chocolate, and lots of hops. I think it is one of the most enjoyable pints of beer in existance. It is also easy to explain by a bar tender. The red may be explained as "it's like dead guy", but your American Brown is explained as sweet, chocolate-ey, and hoppy. A patron will get what they expect, instead of a beer that looks, but doesn't taste, like Dead Guy.
Good luck,
Joe