FakeSMC, the only driver you truly need, is short and easy to build yourself after a look over.
If you're determined to avoid other third party drivers, you can be sure to use only natively supported networking and sound devices.
That only leaves the Clover bootloader, and it's certainly true that this hasn't had an audit/is large enough that performing one would be quite a project. However, it's fully open source and receives quite a bit of interest from across the hackintosh community.
Hackintosh users are also rather small in number and mostly technically knowledgeable; there are far larger and easier userbases to target rootkits at.
Therefore, although I understand your concerns, I am not worried at all about the security of my hackintosh.
>Fedora
Desktop Linux (any variety) is in no way comparable to the usability of OS X. I say this as someone who ran desktop Linux exclusively for years.