LA+0 Vampire Race

[Xefas]

You could pre-choose the invocations at each level, give them a different name, call them "class features", rename the warlock, come up with different fluff, and call it "The Vampire Class".

Noone will ever know spellcasting is involved at all. Mmmm...could convert Eldritch Blast to some form of Sneak Attack progression, I suppose. Not as fast a rogue, but in there...

EDIT: For example, at first level, the Vampire class gets "Children of the Night", an ability that lets them, at will, summon a Bat Swarm, but it only exists as long as they spend a standard action every round concentrating their badassness at it.

At second level, the Vampire class gets "Spooky Nightvision" which lets them see through all darkness perfectly, whether magical or mundane.

He doesn't have to know it's just a Warlock with "Summon Swarm" and "Devil's Sight" because they're always at-will or 24hour constants.