The Punisher already picked up the Capt America guise (sorta) in the the pages of Punisher War Journal the last few months. I didn't complete the whole storyline...but he put on a Capt America outfit to kill a white supremacist who dementedly believed himself the heir of Steve Rogers, the WWII Cap. Pun called BS and fighting ensues.
I do not think the new Cap is Frank Castle. Punisher respects greatly Capt America, the man, and all he stood for. He doesn't feel himself worthy of being the man himself.
THe gun, even if a 1911, is wrong for Cap.
Objectively, it will also draw the scorn of antigunners and the mainstream. Think about it.
Even myself, a bigger RKBA guy than a comicbook nerd--I have major issues of Captain AMerica needing a gun(even if he ISN't product a US WWII supersoldier program). He's CPT America. He can kick ass without one.
My opinion, my favorite version of Cap is the Ultimates one. He does often pick up a gun. He's a soldier. But the gun isn't a part of his uniform. And he's just as deadly without it.
THis will not go well for marvel. This will go down like the elctricty blue/red superman that came about after HE died.. remember that? It sucked.