Please, please, please consider this request!
The ONLY thing holding me back from buying a Monolith and telling all of my friends to do so too is that it has no pocket(s) to hold the power supply or a couple of accessories.
I know that Tom hasn't added that to the Monolith because he thinks people won't need it if it's usually used inside another bag. I say that's flawed logic because what I want to use the Monolith in any backpack but be able to quickly pull the laptop+power supply out in one motion. At work or a meeting, I could carry just the Monolith with me since it could also have the power supply too. The vertical format is not a problem for me, and I am not particularly tall (5'10"). Yeah, for long distances, I'd prefer not to carry it alone in the vertical format, but for short distances within my workplace or from the car to a building, that would not be a problem. When I'm ready to travel home, I would just through the Monolith back into the backpack and go. In fact, I think a Monolith with a pocket or two would be the most versatile and protective slim laptop case available anywhere.
It seems so obvious that the Monolith should have the same pocket on its side that that Brain Cell has. They're both designed to be used inside other bags, and the pockets do not add much bulk when they are empty. I don't know how often I'd use it, but having D-rings on the Monolith would be a nice addition because it would give me the option of attaching a shoulder strap. What we consumers want are the options to make our own choices about how to use the bag. You did an excellent job in achieving that with the Brain Cell but for some reason have remained stubborn on doing the same for the Monolith. Basically, the Monolith and Brain Cell should be exactly the same except for the orientation of the padding, opening, and handles. Take a look at how Waterfield markets its SleeveCase by giving the customer options: horizontal vs vertical, pocket, D-rings, and the type of opening (flap or not; I would suggest always having a flap but offer velcro vs zipper).
By the way, as for zipper vs. velcro for securing the top, I prefer the zipper because it's so much quieters than velcro. If you're in a meeting or presentation, no one wants to hear the loud sound of velcro. Thus, I'd recommend keeping the zipper of the Monolith and perhaps make it waterproof and softer like the Acme Slim bag. That would eliminate the risk or scratching. Another very useful change would be having a light-colored (like yellow) interior for all of your bags, including the Brain Cell and Monolith. It's so much easier to see things like pens if it's not so dark in the bag.
For about 3 years now, I have been "holding out" on buying a good laptop sleeve because I want a hard-sided vertical one with at least one pocket. Previously, Willowdesign offered exactly that with several SlipCase bags, but they have gone out of business are not making them anymore. Trager too had a vertical model of its Transporter, but it is too bulkly for today's slimmer notebooks. The Booq PowerSleeves are, I think, the best option out there right now, but I have not bought one due to their lack of hard-sided protection. Acme will be coming out with a vertical version of their Slim bag sometime this fall. When that happens, they will have the only vertical hard-sided shell with a pocket. Their bags are very expensive, though. You have an opportunity here to simply add a pocket to the Monolith with very little increase in its cost and are best poised to fill this gap in the market.