I take a slightly different view.
Do they need more product? Absolutely. But I think it would be a bad move to sell a sub 30k FWD Cadillac or compact crossover. Let Buick take car of that end of the luxury/premium market. Besides, Mercedes need to do that sort of thing because of CAFE -there are only so many people willing to buy Smart cars. BMW isn't so bad off because Mini does fairly well. And Audi has VW to raise its scores.
Anyways, they need something positioned between the SRX and the Escalade, and a new SRX. Possibly make the new SRX slightly smaller to give more room for a large crossover.
I'm not sure how I feel on the need, perceived or otherwise, for a high performance 2 seater. They need something to make a statement, that embodies everything that the brand can be. The R8 has AWD, clean styling, and mediocre performance. That Mercedes you mentioned is a bully in a 3 piece suit. There is no real BMW halo car, but if the brand were to be summed up in a car it would be the M3.
Now, the important thing is that the R8, M3, and the GT are all similar only in what the represent for their brand. Its unlikely that anyone would cross shop the three of them. But they're each the ultimate expression of the brand. And
that is what Cadillac needs. Is that a Cien type thing? Not really, in my opinion. Perhaps its the Elmiraj/CT6. Maybe, but I don't think it goes far enough. But for me, the car that defines what a Cadillac should be is a 1959 Eldorado Convertible. Bringing that monster back as a 'retro' design would be a epic disaster. But a new car that captures that spirit, I think thats what is needed as brand halo. A big, bold, beast of a car. A car where 'too much' is more of a challenge than a limit. If Cadillac wants to stake its claim in the luxury market, I think that is where they need to go.
Oh, and the new naming strategy is stupid. [_]TS seemed fine, with the exception of XTS (which is probably being phased out soon anyways). You have ATS at the bottom, then CTS, and the 'CT6' would then be an ETS. Coupes would be ATC, CTC, ETC, etc
. No clue what to do for naming crossovers & SUVs ... but then again, I don't know how the CT[_] system accommodates them either.