How big is "Big Enough"?

Let me preface this with a short introduction for those not familiar with the concept of giant robots. These machines are common both in Japanese media (anime, games, manga) and American media, and are generally referred to as "Mecha" or "mechs". These machines vary greatly in height, armament and abilities, but there is no doubt that many believe the future of warfare to be held in the hands of mecha.
I have always had a soft spot for mecha, beginning with my older brother's Battletech hobby, continuing on to a fandom with the Robotech series and many, many other outlets to get my mecha fix. Bearing this in mind, I wanted mecha to figure prominently into Neurojack since they were (and still are) such a large part of what I consider to be a quintessential future world.
If I had to choose, I would say that there were 3 primary influences on the mecha in the world of Neurojack: Dream Pod 9's "Heavy Gear" rpg, Masami Yuki's "Patlabor" anime/manga and Shirow Masamune's "Landmate" mecha from "Appleseed" and a few other of his works.
The mecha in the world of Patlabor are very utilitarian; they are primarily built for construction and police work, with a few military models thrown in here and there. They are small (around 16 meters in height if I remember correctly) and not anywhere near as fast or as well-armed as say, some "Superhero" mecha in titles like "Giant Robo" or "Macross". This made me think of a future where mecha had an array of practical and (compared to most mecha fiction) realistic applications.
Similarly, the mecha in the Heavy Gear world are quite small (the largest top out at around 8-10 meters in height) and are very maneuverable. They serve military, commercial and police purposes (though the story focuses on the military applications of the Heavy Gear) and run off of Internal Combustion Engines. Some of the elements of Heavy Gear mecha design (Crash bars, sloped or angular armor, camera eyes set into the head that revolve on a track, pilot situated in a small cavity in the chest and a few other things) bear a stark resemblance to the Japanese series "Armored Trooper Votoms" which aired in the early 80s, but still enjoys a following. Heavy Gears, unlike many other mecha types, were relatively lightly armored. They carried a rifle in their hands, usually a rocket pack or two on their backs, a knife and grenades. Some heavier models toted mortars or cannons, but nothing the scope of which you'd see on the average Battlemech (from the Mechwarrior or Battletech series which, by the way, ripped off some mecha designs from another Japanese anime series called "Fang of the Sun Dougram".)
One of the latest and most influential inspirations for the mecha in Neurojack, Shirow Masamune's "Landmates" opened the door for a whole new class of mecha. His Landmates were small, fast, lightly armed and armored, but fulfilled a variety of roles, just as the mecha in Patlabor and to a lesser extent, Heavy Gear, did. I particularly liked his designs, which featured very rounded bodies and stylish armor. One unique aspect of his Landmates (which I did not translate to Neurojack) was the concept of "Master Arms"; smaller armored gauntlets that the pilot would stick her/his arms into and use them as they would normally. These arms would in turn dictate the movements of the larger "Slave Arms" that were attached to the shoulder.

Bearing all of this in mind, I set out to build the mecha for my world. Initially, I took a more "traditional" approach and introduced 3 classes of mecha: Ramparts, Artillery and Palisades. Palisades are exclusively construction-class mecha. They are smaller than Ramparts and Artillery, are not usually armed and mount only rudimentary armor. Ramparts were (I say "were" because they are no longer part of the Neurojack world) the cream of the crop: they were quite large (between 20-50 meters in height,) mounted enough weapons to level a city and enough armor to stand up to anything save another Rampart. The only hitch was that they were ridiculously expensive to produce, meaning that there were less than 200 of them on the entire planet. I pictured them looking almost like something out of Makoto Kobayashi's "Dragon's Heaven", but with a slightly more coherent look (not that I dont like the look of Kobayashi's mecha, I just think they look a little disjointed.) Artillery, in the same vein, were meant to be quad, hexa or octo-legged mecha that were larger and slower than Ramparts, but carried much larger weapons.
As time went on, I began to realize that I had made Ramparts out of Illuminus and the people on Asperian were fighting for what little remained of the Illuminus deposits. The question occured: "Would the people spend massive quantities of an already limited resource just to kill each other? Isn't there a more economical way to do that?" So Ramparts got the axe, but I didn't shut one door without opening another.
While reading Shirow Masamune's "Dominion", I began to see the logic in a small and maneuverable mecha package, particularly in an urban combat environment. Thus, I devised the smaller, faster "Drudge Exoskeleton System" or DES. The Drudge is a suit of combat armor powered by a battery and large enough to allow a single soldier to carry large-caliber weapons and enough protection to soak hits from anti-tank weapons. Most Drudges top out at around 5 meters in height and are designed with more fluid combat in mind, rather than epic battles between single machines. Drudges are primarily used by the military who use them as front-line combat units and by police forces who use them as armored units in the modern equivalent of SWAT teams; ARMAS units (Assault/Rescue Mecha Armor Squad.)
I eventually gave Artillery the axe as well, since the focus of the world began to shift away from all-out warfare and towards smaller-scale conflicts that centered mainly around small land disputed in the equatorial region. And so the titans were left behind.
Palisades remained untouched and continued their role as construction mecha, the way I had always intended. More small mecha joined the world as time and revisions went by: Rapid Interdiction Units or RIUs (Drudges with Helicopter rotors on the backs) and Multiped Tanks (inspired by the Fuchikomas, Tachikomas and other minitanks from Shirow Masamune's "Ghost in the Shell" series) joined the scene, each with their own particular role. RIUs fill a need in urban areas for a quick-response unit while Multiped Tanks are used for espionage, urban warfare and some front-line duties.

With all the different mecha that have come and gone from Neuroack through the course of it's evolution, I can't help but wonder: do the giant mecha have a place in Neurojack? I suppose there could come a time when the great titans walk the planet again, but what would spur their production? Something very large and very menacing would have to threaten the people of Asperian to spur the development of such a machine and even then, they would appear in such limited numbers that the loss of a single machine would be a detrimental blow to whatever nation created it.
There is of course, also the gaming aspect to consider: who would want to pilot a scrawny little Drudge when you could pilot the mammoth Rampart? Does the world of Neurojack even need something as big and destructive as the Rampart? Considering the current trend in modern military combat vehicles, the motto certainly seems to be "Smaller and faster is better than bigger and tougher"...would that still hold true several hundred years in the future?

One could also make the argument that this whole thing is somewhat academic, seeing as how I've already written Ramparts out of the Neurojack world and writing them back in would mean another complete rewrite and another change to the Vehicle Construction rules...

Oh yes, I almost forgot. There was one more type of mecha that I originally wrote into Neurojack that has since gone the way of the Dinosaur: the Aegis. Designed to be the absolute last word in mecha technology, Aegis were my attempt to strike a balance between the sleek and very humanoid mecha designs in "Neon Genesis Evangelion" and the weapon-packed mecha of the Battletech universe. The Aegis were very human-looking, but carried enough firepower to wipe an entire nation off the planet, and towered above the battlefield at between 70 and 90 meters in height. It occured to me, as my friends and I were driving through Richmond a few days ago and happened to pass by a 30-story building, that one of my Aegis was as tall as the building. I couldn't help but think "damn, that's tall."

I put it to you: how big is "big enough"? Are Drudges, RIUs and Mini Tanks enough to satisfy your appetite for armored robot-clad mayhem, or would you prefer something that could bring a city to it's knees?