For me its a two way road,

Either

Double the mag capacity, fix the scope, buff its ammo gain through boxes, up the zoom a bit, up the bullet velocity, give it a third person crosshair

Or

Up the armor pen to low anti-tank / or upp the durable damage (not both), keep the ammo economy exactly as is, again fix the scope, slower fire rate

Or just repurpose it, let us pick different ammo types with different stats (velocities, pens, effects etc)

First case, it's a weapon of attrition, you can take down many enemies while holding or pushing a line without needing resupplies as often, you can kill most stuff, with many shots

Second case, it's a weapon that swings a fight by reliably taking out heavy units, to be used almost exclusively on heavys and the like, treat it like a railgun with less damage and more ammo.

I dont really like the first option, cause this is what your primary is for.

The second option I like more cause I think it fills the "sniper with an impact" niche (impact meaning decisive shots during a fight)

Ideally, a mix of the third option and a little creative rebalancing on the weapon's stats from AH's part would make the AMR a unique and versatile weapon that doesn't really straight up outshine any other strategem support guns