Eh, a single dog wouldn't really be any threat at all in the game. Unlike a single Hunter Killer Drone, which is virtually unable to be truly countered. Sure Blind Eye can prevent you specifically from being targeted by it, but you can still get killed by it just by being near someone who doesn't use Blind Eye. Even Flak Jacket doesn't always work in protecting you from it if it hits directly or right next to you. It's almost like a miniature Hellfire Missile as its blast radius is pretty large.
A single dog, however, would be easy prey and probably feel like a waste. Even the entire K9 unit, as long as your whole team isn't a bunch of idiots anyway, is pretty easy to counter so long as people pay attention, look around, listen, or even just camp out in a corner with easy-to-cover entrances.
A fun, high-tier Scorestreak I was thinking of was being able to use the F-38 like you could in the Campaign, similar to how one could use the Gunship in Black Ops I.
It'd also be fun if you could equip a blade like you could pick up in the Campaign (Pulwar Sword, machete, etc) to use as Special Weapons alongside the Crossbow and Ballistic Knight (really, only 2 "special" weapons?) These ones would actually allow people to kill at longer reaches, but it would also have a slightly slower movement speed, slower swinging time and such compared to the knives.
There could also be the Combat Suppression Knuckles from the Campaign. It would actually take 2+ hits with them to kill, but if you hit them, it would have a (much shorter) Shock Charge-like effect, leaving them a little more vulnerable for the follow-up blow(s). But they'd also be able to move faster than the knives, but also have shorter range (as in you'd need to be right next to the person to hit them).
Another high-tier Scorestreak could be the CLAW. Basically, a much bigger, stronger, (and slower) A.G.R.
A mid to high-tier Scorestreak could be giving you 1-2 mortar shells you can throw. Perhaps they could add in the Bear Traps as Tacticals, and you could combine the two like you could in Campaign aside from just using them individually.
Another mid-to-high-tier Scorestreak could be the Optical Camouflage Suit from the Campaign to make you look almost invisible. Of course, anyone with a decent eye will be able to see the distortions, especially if the person is moving. Also, it will NOT be usable alongside Ghost and whatnot as that would be really unfair, and firing a weapon will automatically turn it off and expose you. And people will still be able to see you through a Dual Band, EMP can screw with it, and so on.
High-tier could be some sort of Celerium-based Black Hat PDA will let the user actually hack enemy vehicles, turrets, etc and have them fight for you instead. A penalty could be that you get even LESS XP from kills from them though. Of course, depending on how high-tier it is, it could take a few seconds to work
High-tier could be a swarm of Dragonfires like you can get in the Campaign. All AI-controlled that will go after enemies, shooting at them and all, and there could even be rocket-firing ones among them like the Campaign.
I'd suggest the Storm PSR, but they'd have to nerf it quite a bit to keep it from being otherwise broken or it'd have it quite high-tier. Same with the Titus-6 since you get both a triple shot, sticky, straight grenade launcher and a double shot shotgun in one.
The XM-31 Grenade Launcher (the wrist-mounted launcher) could be a fun mid-tier Scorestreak.
The Kinetic Strike Weapon could be a high-tier Scorestreak. Something akin to a single big mortar call. Bigger blast radius and power, but only that 1 use. Of course, useless in places with a lot of overhead cover of some kind like Aftermath.
....just a bunch of random thoughts.
You can EMP Hellstorm Missiles as well, although it doesn't really help too much, lol. You'll get an 'Intercepted' medal for doing so.
I just mentioned in another thread that I'd like to see a modernized (read: fictional) version of the AC-130 appear, but with the 40mm cannon replaced with a four-shot rapid-fire guided-missile launcher, for which you'd laze targets like from the Lodestar--the missiles would be much quicker but would have a blast radius similar to the 40mm cannon. Perhaps add in an AI gunner that would assist you in finding targets out of view, too. Obviously, this would need to be in the 1800-2000 point range, lol.
In my opinion, there isn't a scorestreak in this game that has the same 'intimidation' factor the AC-130 did. The Swarm comes close, but the ability to be basically immune to it with Blind Eye makes it seem like it has several times more bark than it does bite, lol.
I find that the the sheer numbers (and stupidity of teammates) usually makes up for any sort of Blind Eye blocking. The blast radius for the Swarm is deceptively big, so just being close to it impacting some other random place, or it hitting a teammate near you without Blind Eye, can result in a death for you, especially on smaller maps. (You may as well ragequit on a map like Hijacked, Carrier, Slums, etc, lol.)
I tend to find people panic a lot more when a Swarm is called in (especially early on with a lucky Care Package) than with an AC-130, in which case, 2+ people would spam out their Stingers/SMAWs at it and it'd be dead fairly quickly, especially if they themselves are using Blind Eye (Pro) to prevent themselves them from being highlighted. With a Swarm, it's a lot harder to defend against, IMO. You could hide inside buildings pretty easily with the AC-130 and remain relatively safe, but the Swarm can go straight through windows/doors and blow up in the middle of the room, killing you since it constantly circles quickly above, allowing it to detect anything below pretty much.