Alternatively, if you're going for a single high-powered drone, I'd look at one of the metahuman-sized anthro-drones, upgrade the armor as much as you can, and then have it wear armor on top of it. Yes, anthro-drones can wear armor, and it stacks with their 'natural' armor like a troll's, and can make it so you may be able to survive close combat for a bit.
Otherwise, I'd go with a team of 5 drones as soon as you can afford them. Two up-armored Lynxes with assault rifles, a Doberman with high-power rifle (probably the Crocket EBR), a drone with a grenade launcher, and a flying drone for overwatch with a Barret 122. When you can, get a couple smaller drones for clandestine recon inside buildings. Yes, the individiual drones will be weaker, but along with your team there will be more targets to spread the damage, and having overwatch means you can try the whole 'shooting first' thing.