[quote]the last major concern I have is that the 'Mechanical' should have a clear advantage over, say, a super-tank or even an ordinary tank, so as to answer the question of: 'why not just use a tank'?[/quote]
It really isn't supposed to. The idea behind a physical control harness was developed for salvage rigs, powered exeoskeletons and such. It was never intended as a combat platform. Compared to a neural link, it is meant to be inferior in virtually every metric. If there must be an answer to that question then though I'd say this: Tanks require a crew of 2-4 people generally plus training, but fielding an equivalent armament on a humanoid form that uses direct movement control requires one person with far less training to be similarly effective.

[quote]Tanks, APCs, and IFVs can bring down a 'True' NC if used in enough numbers and if said NC is alone.[/quote]
Not even a badass mecha pilot can override the Law of Gross Firepower.

[quote]Aren't pilots supposed to be part of Electrum Company? Is she being contracted out by Tshwane Mining?[/quote]
I figured that would be assumed. That's the correct assumption that she's officially on loan.

[quote]also, I kinda pictured Sync-Rating as a measure of some kind of NC signal integration into brain function or something like that. Lore thread says 50%-sync is the lowest viable, but does that mean low-end pilots use Mechanical control methods like Mira does, or is the implication that 50% is required to fully mentally control an NC?[/quote]
You're on the right track. A 50% sync is the minimum to fully control a mech through a neural link. Since pretty much all mechs everywhere are built with full neural interfaces, it's also the minimum to be a pilot. Mira would never have been accepted as a pilot had her overinflated reputation not preceded her. However since she had the opportunity, she found a way to cheat.

I've made the assertion that if you reduce the amount of information travelling over the neural link, the reduced load will inflate the synchronization of the pilot. In Mira's case, this boosts her sync rating high enough to achieve a viable interface. She still has some tactile feedback coming over the neural link but the primary movement control and weapon firing is handled through the physical harness. This makes Legion unique in that it's a hybrid between neural and mechanical interfacing. This hybridization is the reason that Legion is a viable low-sync mech despite relying on the inferior mechanical control harness.

It's theoretically possible that another hybrid combatant mech does exist somewhere, but it's equally likely that Legion is the only one of it's kind and Mira is the only viable hybrid pilot in the world. By all account she should never have been a pilot in the first place.