Buying a 9mm 1911 is like buying a V6 Mustang. That platform was designed to work best with a heavier power source. Much like the Mustang never really being made for the V6, the 1911 really wasn't made for the 9mm. If I wanted a car with a good 6cyl engine, I know that a BMW or Porsche is the best way to get a top quality 6cyl engine. They maximize the capabilities and characteristics of that powerplant.
In much the same way, the 1911 is a big heavy gun designed to shoot the .45. It's a large frame pistol, and it really only fits to shoot .45ACP or 10mm Auto from it. If you want 9mm, there are numerous other platforms out there that are better suited to take advantage of the 9mm platform. You will only have 9 rounds in the magazine or less, and you still have a full size 1911. A full size Glock or S&W M&P9 has 17rds in the magazine, and is going to be a little bit smaller in size than the 1911, and will be much lighter as well. An even better backpack gun is Glock 19, G26 or M&P9c, or get a compact XD. If you're in a Bugout situation, you really want efficiency. Efficient is spare 17rd or 15rd magazines, not a whole mess of 8rd and 9rd mags.
The other big issue is reliability. 1911s are less than reliable pistols. I'm not sure if you have any experience with 1911s or not, but for anyone here reading this that does not have much experience with 1911s, they're not a novice pistol. You have to know how to take care of them, know how to diagnose problems, and either be able to do your own gunsmithing and tuning, or be willing to shell out the money when the time comes. There are quality brands like Springfield that make great 1911s that are robust and pretty reliable (for 1911s), but they still can't touch the reliability of your average combat pistol like a Glock, S&W, HK, FN, Sig, etc. Those are guns that can get dirty, wet, cold, dusty, sandy, salty, iced up, blazing hot, etc. and still perform reliably.
Just my own thoughts on the matter.