As for designing a mech that aims with its body, that’s how I originally designed my mech '99. It does do a lot for keeping your c.g. low not having the big heavy turret up high on top. I was always intending to got to a split target plate design as well… but never got to it.
It works really great in AZ. I found that always walking the direction your shooting really helps on keeping a sense of direction and not getting lost. There’s also a cool down rule per target plate, so it tends to keep the front plate aligned with your enemy and not giving them multiple target plates to shoot at.
For EL it works OK. You’re limited in how much elevation you can achieve by the the length of your legs. Also for high elevations, it really shifts the c.g. and weight balance messing with the walk. I found if your fighting a tall mech, you couldn’t reliably aim/shoot at the same time. I would have to separate the two functions… aim at a high elevation, shoot, return to neutral, move, stop, return to high elevation, and so on. For mechs low to the ground, I had no issue.
In later incarnations of '99 and on my new mech GS Marauder, I still aim AZ with the body but have gone to a single axis turret for EL.