As for the Pacifier, the main issue I have with caliber upgrade is that SR uses a caliber system where all weapons of the same class (Heavy Pistol in this case) use the same ammunition (meaning they must be the same caliber by extension).
It's just a simplification for easier game play and one that i would personally never use.
Infact i would laught for minutes if someone succested during a game that their going to take the bullet from their predator and load them in to their Warhawk or from their PSG enforser and load them into the Barret.
However, it is one of those things that is inherent in the game as it stands, just as spells causing drain is. Personally, I think the sourcebooks have done a decent job of avoiding the 'power creep' you see in some other games, where everything constantly gets bigger and badder and better. With a few exceptions, everything that is under availability 20 has stayed at a fairly stable power level even from the original SR4 book being out. The new books have offered increased versatility (You have your Steel Lynx, or there's that Crimson Samurai, or that Hachiman), and cosmetic changes (I, for one, love the color-changing enhancement to clothes in Attitude). The newer options (under availability 20, again. I haven't had opportunity to play with any of the uber-gear.) all are about the same power level as the older ones.
Adding in something that inherently increases the power of a handgun to do the same damage as a sniper rifle just runs counter to the way the entire rest of the game is set up.