I got access to blackops stuff pretty quickly after Promotion 2.
Its hard to see past the blackops sniper rifle at the moment.
In fact most weapons you gain access to at P2 look worse than what black ops have on offer. I never really got past hunting rifles.
Maybe black ops stuff should take slightly longer to get?
I wouldn't say they overall replace all the Promo II stuff, as weapons like the OICW has no equivalent (well the Lc, but it is a joke ) and BO assault rifles are worse than the G11 due to being slower at firing. By Promo II I usually use:
Pistols: Mk23 Socom due to being common enough and having enough punch against more armored enemies. BO pistol is better due to more ammo and slighly better snap , but they ain't much difference. Although really pistols imo are better as backups comapare to smgs, so even the more weakly beretta can still be used against black lotus or Dagon. I'm not a fan of hand cannons overall, but I prefer the Deagle over the magnum at this point, or the Widley on high acc soldiers against less armored foes.
Smg: BO submachine gun is pretty good and replace the machine pistols (skorpion, rak) in being portable enough and providing a lot of firepower. The Big Mac 10 is also an option althought frankly I find it to innaccurate. The other smg I used is the P 90 for less accurate agents as it's accurate, doesn't take a lot of TU and has good ap capacities.
Shotguns: Black ops all the way, first the BO shotgun and then the CAWS.
Rifles: G11 basically outshines everything else due to the reasons above, but also the OICW provides reasonable firepower while being long range enogh. BO rifle ain't that spectacualr without tritanium, and the BO assault rifle is a bad rifle overall.
Snipers: SVD and Bo sniper rifle. Bo sniper rifle is slighly better than the PSG-1, and in hands of less trained agents the .308 is better. SVD are much better than the auto sniper and really shine as reaction fire long range rifles, hiiting like a truck.
Other BO weapons include the spypistol(worse imo than the snub revolver) the miniguns (ligth one being okayish close range weapon, big one being a massive overkill), the machine guns (which IIRC the smart one isn't avatible early, so bad weapons overall) . So in summary I would say BO weapons complement, rather than replace standard weapons and really they ain't massively better with regular ammo compare to standard guns.