^ I Don't know, I never tried it but Temporal Manipulation triples pistol's power.
That being said, ability to dominate everything in sight during 1 turn is so good in this game so such build should work. It would require some additional tricks to handle content, fortunately high Dex means you can get most of your grenades. I would add Grenadier, Three Pointer, possibly Sure Step, and Sprint. Typical fight would start with grenade or two, caltrops, Aimed Shot to the face, hide from line of sight, enemies come closer, next turn activate Bullet Time. I would reduce either Int or Perception and max Dexterity, possibly going into Versatility (probably not though, I hate Versatility, but still...)
As for SMGs, they are extremely viable with or without magic but I hate them as much as Versatility. Low hit chance + extremely high ammo consumption + low range + boring 'burst burst reload burst burst' playstyle = not fun for me.