Capacity: Para addressed that 30 years ago. Para is gone now, but half a dozen companies sell double-stack 1911s today. Bul even made some in the same plastic Glock uses.
Caliber: 9x19, .40 S&W, or .45 ACP, just tick the right box when ordering.
Thumb safety: still a point of jihadi-level contention, but I note there's no 1911 equivalent of "Glock leg."
Reliability: Real Colt or licensed production vs. Sig or Glock, or some random parts-bin cheapo vs. a Pakistani-made Glockalike? Or are we talking about a "boutique" 1911 so tight it won't cycle when it's dirty, and even when clean is fussy about its ammo? The 1911's reliability was proven by the original Army acceptance tests; someone else's "interpretation" of the design a century later, who knows... Doesn't matter what type of gun it is or who made it, the reliability requirements should be in the purchase contract. Sig has been bitten *hard* by that a couple of times.