Stowable and lockable bed extender?

Just wondering if the unicorn of bed extenders exists - here's my perfect set of features (in no particular order):

1. Stowable or foldable to the side of the bed (much like OEM ramps)
2. Lockable when stowed (cable lock is fine, but a neat built in Box Link jobbie or something would be cool)
3. Usable as, preferably rectangular, bed extension (this is way place the OEM plastic folding system fails me).
4. Does not impede the liftgate flatness (I've seen a few that require mounting a base plate or fixture to the tailgate).
5. Non-strap based mounting when in use as an extender (rigid clips, plates, etc, are preferred).
6. If side-stowed they need to fit under an aluminum roll cover. I have the Syneticusa from Amazon and for the price it's absolutely awesome - certainly not as nice as my previous Truck Covers USA, but also less than half the price.
7. BONUS: usable as ramps
8. BONUS: black to match the interior of bed)

So far I've found:

• Top Line Fold-Down Bed Extenders BX4004-02 - Not foldable to the side, but it does stow... kinda bulky when not in use due to its curved shapes, though. Could be locked in place by changing the pin removable system for something else. Not usable as a ramp. I wish the mounting plate on the tailgate was totally flat.
• ReadyRamp - These look great but it doesn't stow, which is a bummer. This also seems to mount in place using straps, which I find annoying.
• Extreme Max RampXtender ATV Ramp & Tailgate Extender - I owned the fitted pair of these and loved them for the most part, but they were way too bulky when stowed. The strap mounting was annoying. These got jacked from the back of a previous truck under a cover that got jimmied open (that's all the stole... quick crime of opportunity I believe).
• "The Quick Extend-A-Bed" seems to be a prototype that never got made. If I could buy this for like $300 I would.
• DIY PVC pipe. This guy here has the cleanest one I've seen which is very affordable, but doesn't stow and doesn't work as a ramp. I could probably modify this to stow neatly.
• X-Treme Gate XG-001 doesn't seem to be in production anymore... also it is crazy expensive as a $500 plastic extender and it's obviously not a ramp. I like it's stowing abilities, though.

I think the perfect option would be the OEM stowable ramps but modularized into sections that somehow clip into the bed latches so they could also be used as an extender as well.

Any other extenders out there I should consider? Thanks!