I've kinda thought about this a bit and, well... my idea is a mech that is, for all intents and purposes in canon, an experimental weapon platform with unique primary weapons, in the role of a variable support mech.
The secondary would be something like the G2 Assault vulcan, however.
The first primary could be some sort of chargable flak cannon, but the charge would load in an extra shot, so it would basically shoot 1 or 2 slightly narrow coned flak shots at a time. Something in the close/not quite mid ranged set. Perhaps one of the double shots would do less damage than a single shot, but both shots do more than a single shot.
Alternate could be a Rail Gun that can fire through walls (to a point) or does full damage through a turret shield, but has a relatively slow RoF and only so-so damage. Kind of a support mid ranged sniper, scaring enemies out of cover all the while not making it a weapon viable for actual 1 vs 1 duels.
Prestige would be a fairly accurate needle gun type that fires a bolt that soon explodes, causing decent splash damage after a second. The Needle itself would do minor damage. Something to slightly spook tightly packed mech groups.
It's ability would be similar to the Pred's, without the stealth. A noticeably enhanced walk speed (faster than pred) and Pred-vision. Similar cooldowns and skill limits as well.
As for stats, I'm thinking B-Class. Overall average but has an above average radar (aid in tracking opponents), lower than average fuel (better walk speed at the expense of fuel capacity) and above average cooling.
And now I await people who will go NO TOO OP.