It is possible but difficult. A member on fj went 14.2 I believe with a cold air, header, FSW 2.5" exhaust, drag radials, tune, LSD, and weight reduction on the extreme in a ZX3 with a 2.3L. This was also at what some consider to be a fast track (Cecil) in a colder part of the year when the air was more favorable. With the 2008+ models being a bit heavier and with the 2.0L, I don't know. You would probably need the Cosworth manifold to get there.
I know it's not what a lot of people like to hear but by the time you buy everything you would need to go mid-14s NA, you could buy a used turbo kit + tuning and go mid-13s. NA will never give you the same bang for your buck, unfortunately.
I didn't put any money on NA parts. I saved up and went turbo from the beginning. My first mod to my car was the FSWerks stage 2 turbo kit.
2007 Focus ZX3 - FSW Stg 2, cams and cossie mani, stock motor, 7.74 @ 93mph (1/8th mile) w/ 1.84 60ft spinning
Built motor on the engine stand!
Shout out to FSWerks and Focus Rising 2012!