Why do people then buy 2/3rds of the E classes in V-6 guise? According to your theory they should go for V-8, given more prestige, not caring about fuel economy which is not different anyways according to you.
This sounds more like an excuse statement for Cadillac trying to wiggle its way out from not being competitive. Tell me how much history XLR has to justify its halo nature, or having a trend which people will not be willing to give up? None. Which means it is more capable to try something out of the box and be innovative. Oh it is a Porsche does not mean anything, but trying to out do a Porsche with the same powertrain criteria and level of refinement and performance from a company that built land barges will mean something. Isn't that what Nissan did with its GTR against the 911 Turbo? With your argument that people will not buy a Cadillac because it is not a Porsche, why would they buy a 620hp Chevy over another exotic? Don't build it then.
You better make that as the V version then, because based on your notion, it will be said, oh it is a BMW Z4 and MB SLK, Cadillac will have no hope of knocking off those, it has to deliver a car that has to be so much better than them for $20k less that it will not be funny.
You misinterpreted my statement. You argued that with $7500 rebate a N* V8 will cost almost same as the V-6, then why would anyone want a V-6. In that case you are assuming that V-8 if continued in production will continue to have that rebate and that V-6 won't. I put $6,500 as a number, it can be anything. The fact is if you claim that XLR is bad in resale, nothing is going to help it, not even putting an engine made of gold, till you fix the image up. Smaller engine most of the time brings in volume and putting a V-6 may bring more cash to the platform which will help GM's coffers. As you mentioned the people buying these cars do not care about gas, and other intangibles, will they care for the intangible of depreciation?
Why build the car then, if the initial market research is as negative as you think, GM should not build XLR. If Hyundai had the same mentality they will not have build the RWD, if Toyota had that mentality they would not have formed the Lexus division, if Chevy had that mentality they will not be building the ZR-1. Instead spend that money to increase R&D and Marketing of other vehicles. The same was said about CTS that it will not out do a BMW, or a Lexus, yet the second generation went by and has won raves. Can't that be said about the XLR? XLR is on a good platform it needs tweaks and a makeover to justify its luxurious pretensions.
The 3.6 DOHC weighs about 350-370lb, does DI add about a 40-60lb penalty? The N* in XLR weighs 432lb.