Pertti Munapirtti, on 01 December 2014 - 01:19 AM, said:
I felt the need to respond at length, because these claims are completely absurd.
Modern tanks are remarkably fast and agile for what they can carry. They aren't significantly bulky for combat purposes -- most have a height less than 3 metres (BT mech and tank sizes are absurd, too), and other AFVs with modern FCS can hit targets that size and smaller with relative ease. To planes or ATGM teams it hardly matters how bulky the target is anyway; if it is plainly visible, it's likely to be destroyed. Not all modern ATGMs even need LOS.
The ground pressure of a tank is very small compared to a bipedal mech (unless the mech would have built-in skis or snowshoes?). They aren't very fuel efficient, but neither would mecha using current technologies be. Future tanks can, after all, utilize future technologies.
Tanks require 3-4 operators because it is more efficient. In most modern (~1970s onwards) tanks, the commander and gunner can spot targets independently, and the commander can automatically slew the turret onto the target he has spotted. Often the TC can also fire the gun(s) independently if the gunner has no LOS or is disabled (redundancy!).
As for APFSDS rounds being useless against mechs, a) the claim is false

it isn't the only kind of round tanks carry anyway. Much like a tank, a mech can be disabled without killing the crew. Tanks can take APFSDS hits to road wheels, tracks, optics, etc.-- these will be damaged and may or may not effectively disable the tank. Similarly a tungsten rod passing through a myomer muscle or joint
will damage it, the effect being largely the same (although a mech would probably have fewer redundant components). The mech cannot carry as much armour in general, so the bit about the cockpit being better armoured is rubbish. It can also still be disabled through hits to the extremities/cameras/periscopes/what have you, and with less armour overall that would only get easier.
I have also heard a ridiculous claim that APS (e.g. AMS) would somehow be more effective mounted on mecha. I have no idea what this is even based on, as a mech of BT proportions would certainly need to protect a larger arc to have a chance of e.g. protecting the legs.
Powered armour or exoskeletons would be useful to teams having to carry heavy loads. ATGM teams could carry more ammo, one man in a mortar team could carry the entire weapon, light radar equipment (still ~200 kg) could be moved with ease. They have little to do with the viability of BT-like mecha.
To answer the question of the OP, I'd go with the Bushwacker. It has a helicopter-y chassis, so it wouldn't look terribly out of place. It still wouldn't be viable, but I do like mechs.
Sorry, but your entire argument hinges on the assumption that Mechs would be the same ridiculous size as those found in BT.
You're wrong, and so is half your argument.
At best, a Mech would reach 6m in height. The two most effective designs would be A) A reverse jointed "chicken walker" scout, and

A bipedal/quadruped combat chassis. Reverse jointed leg configs have already been shown to be capable of incredibly high speeds in testing, and a bipedal/quadruped design would provide a level of mobility a tank could never match. In fact, a quadruped Mech could swap from forward motion, to sidestepping, to reverse motion without ever having to stop. A tank can't do that, it has to slow down, turn, then stop, then begin going backwards. It's inefficient in the extreme compared to a quadruped.
Tanks aren't crewed with 4 people because it's efficient. They have 4 crewmen because it's the only way to effectively operate the tank. More crew means more people to do maintenance, field repairs, and less jobs per soldier. The sad part is, the driver can barely see where they're going, meaning the TC has to direct the driver, command the tank, mark targets, and do 80 other things. The loader is also the radioman, meaning he has to load the main gun (while waiting for the ammo door to move half the time)
and fiddle with the radios to keep in contact with friendly forces. The gunner has the easiest job from what I can tell, he just sit in his little chair and stares through a scope, shooting whatever the TC says to shoot. Well, and the gunner has to remember to switch the targeting computer to the round he's firing (go from HEAT to APFSDS without swapping, and watch your flechette go in to orbit). The only reason we don't use a 2 man crew (TC and driver) is because maintenance would be a hassle, it would overload the crew, and if one guy gets knocked out you're screwed.
Mechs would be mainly automated. The programs exist to keep it balanced, make it walk, and even adapt its footsteps to terrain. You'd have little sound and no smoky emissions to give away your position, other than thudding footfalls. You can carry a reloading AGM-114 launch tube firing tandem-heat and thermobaric missiles from an internal magazine. Each arm would mount a high-caliber autocannon with a loading system that allows you to swap ammunition types on the fly (like a Bradley). In addition, you could mount a small recoil-dampened 75mm field howitzer on a shoulder, or even each arm if they're strong enough. Set the control scheme up to mimic BT cockpits, with the ability to swap the joystick and throttle positions (for weird people and lefties). Control the arms through head motion like a multitude of modern helicopters do, to allow for accurate aiming and target acquisition. Slap a modified CROWS mount up top with an internal magazine feed, load it up with CIWS targeting protocols, and mount an active scanning system to detect incoming projectiles (while doubling as radar for the Mech). Use the same target selection protocols for the modified CROWS turret to allow it to fire on hostiles in your rear arc, preventing some jackarse with a bomb from ruining your day. Legs like those found on an HBR or SMN, would make the Mech much harder to disable with a leg shot.
ALL of this would be in a package not but 5-6m tall. One pilot, same weight as a tank, same armor as a tank, but MUCH more nimble in urban combat situations. Tanks would still be superior in open combat, due to a small profile and whatnot, but Mechs would just be better in an urban environment. You can't use the "tanks mount more armor" excuse for a vehicle the same size as a tank (if you stood the tank up and shortened it a little). At this point, the only advantage a tank would have is a low profile!
As for ammunition, the only other rounds you carry are basically HESH and HEAT. A little spaced armor section ruins HEAT, and HESH is useless against... well anything that isn't a building. If you've got tandem-HEAT shells, then everything dies when hit, simple as that. APFSDS is the primary anti-armor round used by modern armored units. It leaves a quarter-sized entrance hole, and sucks the crew out of the quarter-sized exit hole. For American APFSDS, the round will also splinter on penetration, and cause a firestorm inside the tank due to the pyrophoric action of the DU, setting off ammo and igniting any flammable material. If there's no crew, the only useful bit is the splintering and pyrophoric action. Which, as it happens, is useless if the internals are flame resistant, and the splinters don't hit something useful (like a control system cable). Your argument is also foolish in that it assumes Mechs can't be redundant or armored against such things. And yes, the cockpit would be heavily armored in a realistic 5-6m tall design.
Essentially, anything that could kill a Mech can just as easily kill a tank. I'm under no illusions that giant BT-scale Mechs are feasible, but small Mechs can and would have a place in modern combat.
I think I've addressed all the useful bits, I look forward to your reply.