I've toyed around with this idea for a while, a few people who wheel with me know I have been planning to get around to doing this to my own vehicle.
The OP's linked product though is poorly designed and engineered for the following reasons:
-The MOLLE attachment pattern is a very generic one that limits attachment & ease of use.
-The attachment points are suspect, while you could conceivably place 20~40lbs of MOLLE equipment, it is all weighted on a single
factory coat hanger hook and then anchored into plastic paneling. In the event of an accident that could easily break loose and become a projectile.
-The fact that the MOLLE plate itself is the frame is also troublesome as with that many holes (despite being steel) it will be very floppy with weight on it.
I've looked into doing this for my 4th Gen 4Runner and actually have the tracings/measurements from the 3rd quarter window area (as well as a 5th gen) and have tinkered with the idea a bit. Unfortunately it's all mostly scribbles in a notebook as life has been a bit rough lately and I haven't had the opportunity (or motivation) to get to TechShop to knock out a prototype yet. I do have a rough design with a MOLLE pattern that I'd like to waterjet cut and test out on the 4th gen first; interestingly enough, the 2nd~5th 4Runner 3rd row windows are very similar in general design and shape that theoretically if you have the tracings and measurements a generic "platform" could just be slightly modified to fit multiple generations... (another casualty of Life along with my disconnecting sway bar project that was pushed onto the back burner

)
[MENTION=89562]bimrunner[/MENTION] That is an absolutely bad ass design. I don't know how viable it is for the 4Runners because of how our glass is; but that is a beautiful work of art right there with a lot of thought and engineering behind it!
Post Note-
I have tried to get SpringTail Solutions to show some interest in the 4Runner line like they have the FJ Cruisers and Jeeps, but they gave me a generic line about "not enough market potential, we don't see the point in the R&D."
Their products are really good and I LOVE their rip-away MOLLE packs; but honestly it seems they get most of their money from Government/LEO/Fire contracts than the few off-road vehicles they have products for. So I understand the reluctance to invest in that.