Keep Cadillac In Detroit
Of course moving to NYC may change the players because once Cadillac folks realize that they will no longer be able to afford those 3,000 square foot houses and end up in an exorbitant, tiny apartment.
So here's a suggestion to Cadillac. If you really, really want to go toe-to-toe with the likes of BMW and Mercedes stop badge engineering. Yes the ATS is a good car (or so I've been told, I've never driven one) but it is no BMW and never will be unless GM gets serious. That isn't going to happen just because they move to NYC. It may happen if and when they build a rear-wheel-drive vehicle with an engine specific to Cadillac.
You want to know how to build a world beating Cadillac? It's easy; either give your designers and engineers free rein to build a car, just one model, that wows the world. If you cannot do it with the talent you have right now, right in Detroit, maybe there is no hope. I refuse to accept that though. I know there are extremely talented people at GM. Heck there are even components on the shelf that could be used to build a Cadillac to beat the competition.
Ford went through this in the '90s when they moved Lincoln to Southern California. It really didn't do much for them did it? And Lincoln is back in Detroit (not that Lincoln has found their way yet).
The same can be said of Chrysler and Ford (much less Chrysler than Ford) even though they aren't moving to reinvigorate their companies.