[Android Q&A, Help & Troubleshooting] es0tericcha0s:
Welcome to android. :)

Many of your wants and needs can be met by using the mod called the Xposed Framework. This little guy allows "hooks" on to various calls to the system and redirects them to the Xposed Framework and the modules that you add to it. With this enabled you can do everything from stop ads to mod the status bar, lock screen, themes, and so much more. One caveat: This is currently not working with ART runtime, but not likely you are running that anyway on the One yet. It's also already included in your rom.

Notifications from a a Pattern/PIN/Password locked screen:

http://gs4.wonderhowto.com/how-to/a...protected-lock-screen-your-galaxy-s4-0149781/

(yes it says for the GS4, but the module is listed to work with the One as well) http://repo.xposed.info/module/com.labtech.mod

Custom Gestures:

Lockscreen -

HTC Gesture Modifier http://repo.xposed.info/module/com.mohammadag.htcgesturemodifier

HTC Sense 6 Toolbox http://repo.xposed.info/module/com.sensetoolbox.six

Anywhere but Lockscreen (unless you use a custom LS) -

Gesture Navigation + Multitouch Gestures http://repo.xposed.info/module/ind.fem.black.rayyan.xposed.gesturenavigation

All in One Gestures https://play.google.com/store/apps/details?id=com.phoenixstudios.aiogestures

GMD GestureControl https://play.google.com/store/apps/details?id=com.goodmooddroid.gesturecontrol

Tasker:

http://tasker.dinglisch.net/guides.html

MultiWindow:

http://repo.xposed.info/module/com.zst.xposed.halo.floatingwindow

http://repo.xposed.info/module/com.lovewuchin.xposed.xmultiwindow

Different interpretations of multitasking. There are also tons of different side bar type apps that you can access from swiping from an edge of the screen to activate shortcuts to your favorite apps, contacts, settings, recents, etc. that are accessible from anywhere but the stock lockscreen.

Swipepad https://play.google.com/store/apps/details?id=mobi.conduction.swipepad.android

Glovebox https://play.google.com/store/apps/details?id=com.fb.glovebox

Sidebar https://play.google.com/store/apps/details?id=com.rootuninstaller.sidebar

And so on... (my fav is Swipepad, especially after the last update which improved the performance greatly)

Floating apps:

Sorry, don't really use them.

Custom Sense roms:

Not saying Viper is the best, but you won't really find much that will be MORE customizable than a Viper rom. There are a few on the same level though, such as InsertCoin, Renovate, SkyDragon, and RayGlobe currently.

Lockscreen:

You can enable adding widgets (also in Settings > Security) and the AOSP lockscreen (like on a Nexus device) from the Venom Tweaks app as well. I like some lockscreen apps, like WidgetLocker, but at the end of the day, the 3rd party lockscreen replacements are either lacking in functionality(there are some that do have good security options, most do not), use more battery power, and end up lagging because when you wake the phone it might take a sec for the app to turn on as well where typically the stock lockscreen will be instantaneous. As far as Notifications - well, the phone has that option too, under Settings > Security > Notification Settings. Another alternative is some like Metro Notifications https://play.google.com/store/apps/details?id=com.nlucas.wp7notificationslite which displays notifications a la Windows Phone style (and iOS) as banners, giving you options to swipe to dismiss or click to launch.

Hope that will get you started on your quest. :)