First thing I did after root... Install Xposed framework then download/install the GravityBox(KK) module. In the GravityBox settings, go to Navigation Bar Tweaks. Enable the master switch, then check the box to "always show menu key".
This will enable your menu key and still keep your recent apps key. You can also swap the recent and back button (if your used to that type of layout). And if you want even more then you can do like I do...
(in the Navigation Key Actions menu, not in Navigation Bar Tweaks)
*shrink the nav bar to 75% height
*long press back to close foreground app
*long press home to enable/disabled screen rotation
*double tap home to show a custom app launcher menu (put your fav apps n here)
*double tap back to switch to last open app
*long press menu to enable/disable flashlight
(this is just my setup, each keys long press and double-tap have multiple options to choose from)
With gravity box you can do a whole lot. You can change your battery icon to a different one but be sure to go into your phone "settings>personalization>status bar icons" and uncheck battery. If not, then when you restart you will have 2 battery icons (stock & gbox battery) in your status bar. Also, you can turn your status bar into a brighteness control, which comes in very handy, or enable song skipping by long pressing the volume keys (when the screen is off).
Just check everything out in gravity box, it has soo much to offer.