This is extraordinarily interesting to me on a number of fronts as I am an engineer, I am an artist, and I am also a published author. So I am a mashing of all these things and I also have the worst affliction of all: I need to get things right which is just the way I am.
Al and I had a fascinating conversation earlier today in that he quite rightly said that as a SF writer all I have to do is create a sufficient state of belief in the reader, so it does not really matter if the science I use is not entirely factual. I of course need to future proof my writing, give myself a running chance with the train spotters and of course the engineer in me screams loudly if I stretch things too far subsequently I do shit loads of research and get the science as right as I can.
And a most interesting aspect of this is that the readers who do not read SF, but have read mine, love it and they say the reason why is because it is all totally believable.
So, Mega tanks. For the gaming world they empower the gamers to get bigger, meaner, faster and harder hitting without any of the grit blood shit and nastiness which is actual battle.
Subsequently I believe that we are all right. The games developers get what they want, massive, noisy, exciting machines, the artists get the visual thrill and the engineers who will spend inordinate amounts of time figuring out if these superb looking machines can actually be made.
Who will Al sell these designs to? Probably me. I will take them up and incorporate it into a future story about megalithic structures and of how ultimately they are the expression of power and money because they are good for television. In my stories the battles are all created for AV and controlled by a corporate group called The Games Board who play all the angles to maximise profits and subsequently create social control. So mega tanks are good for the AV market because they are huge rumbling monstrosities that can level city blocks with a single shot. Then of course me as the writer and me as the engineer has to find a way to wreck them. And that I like as I will have to think hard about it and of how to compromise them in an inventive way. Also they fit beautifully into a document that I wrote called "The Articles and Rules of War" which all parties in any conflict have to adhere to or they do not get paid.
Swamp Thing I really like your idea of a huge carrier vehicle with perhaps dozens of smaller little tanks and maybe have them working as a hive mentality. Oh and blades are the extension of the killing hand whether it be meat or vegetable. They are the tool that allows us to eat.
Now, the interesting part of these discussions. What is a beautiful weapon and why do we like certain shapes? I believe we like them on a base level in that they remind us of the human form.
Look at any weapon, vehicle or structure that appeals and then overlay the form and sweep of human form onto them. The curve of the lower back, the sweep of the thighs, the ankle, the multiple forms and structure of the face and so on. We like them because we can relate to them. Plus all those shapes and forms that we see and know off from our environments, those thing we are comfortable with.
Al your question of how will an AI design a building? I believe that you are quite right: they will do a wonderful job. Not because of what they are but more because of what we as humans impart to them as we build them. Your question of an alien's design ethic and of what they would find appealing is a huge and most interesting question.