Imo, you got to go with Vile Weaponry, and Taste for Blood for a serious bleeding character. (That rules out SMG shrapnel bullets, as they do not work with Vile Weaponry.)
So, serrated knives, liberal use of bear traps, this means high dex melee build. Quick Tinkering is a must. Possibly Versatility and an Xbow with bleeding bolts? Also possibly a lightweight bladed metal armor? That requires high STR, but it is not bad to up the base knife damage for a bleed build, although you spend many ability points.
I vest into throwing skill and crowd control like throwing nets and flashbangs, to immobilize and incapacitate while the blood flows, perhaps.