I think you are making it too painful to be so strict to get exactly what you want, here is how it was explained to me when I tried to get a Toyota Yaris with non-standard options. i don't think Lexus is any different.

Basically they crank out these pre-configured cars for dealers to sell, so you get the best deal buying something already at the dealer.. They have to do custom manufacturing to put something non-stardard... oh like power windows on base model Yaris, or, for Lexus, Luxary package on a IS250. It takes forever or they might not build it at all.

I specified everything I wanted, signed something that I will pay $500 over invoice with the fleet manager, fleet manager did say sometimes Japan will say we won't build this. He said he faxed in my order a few times and heard nothing back.

You don't have agreement on the exact price, I think you won't get a very good deal, maybe like MSRP on the IS250 + luxary package price? Considering IS350 you get the Luxary package, it's not that bad of a deal right?

I would have loved the IS250 if it had the Luxary package though, at first I thought these cars all have the memory seats etc but I was wrong.