When reading the how-to's on Nanbackup, they're all talking about first root my Nexus 5 and I need a "Custom Recovery" installed. Isn't that just as "dangerous" as installing Cyanogen? Not saying you're not right, just trying to understand.
In theory, they carry equal risk.
In actual practice, installing a custom recovery has dramatically far less risk.
The main thing for installing either a recovery or a rom - the softwares are NOT generic, only install the ones intended for your make and model of phone, and follow install instructions exactly.
The recovery lives sort of parallel, sort of underneath, the rom.
You can often boot your phone and run normally even if the recovery is in error - provided it was intended for your phone.
Recovery installs with a really simple command window command if you install just our Mini-SDK -
fastboot flash recovery name-of-recovery-file
There are also handy tool kits just for the Nexus that you can use instead.
I prefer the Mini-SDK for everything because I trust me.
http://androidforums.com/threads/adb-guide-updated-2014-11-11.443072/#post-5389081
Follow the procedures exactly as given in the Nexus 5 All Things Root forum, and whether you go Mini-SDK or tool kit, you're going to have trouble screwing up recovery.
Note also that from time to time, a rom may insist on being installed with a particular custom recovery.
That's perfectly normal. Just install as directed so all of the pieces fit as directed.
A custom recovery is absolutely a root user's best friend.