There's no way Capitol would let her do a full on Acoustic album.

An Acoustic EP for the fans, or a bonus disc of acoustic material or a one off release, sure. but a full on album? No.

Wasn't there an article about some Capitol meeting or something that mentioned they wanted to get a new Katy Perry album out as soon as possible after Teenage Dream to ride off it's success? Can't really remember now, it was a while ago, but it it's true there's no way they're gonna let her waste months working on an album that wont be commercially successful.
And her voice doesn't suit country at all. Bullet sounds much better done by Jessie James or whoever it is that it was written for. It isn't strong enough to carry the song. (Yeah, it's good to fans - but commercially? Nah.)