IIRC, in Dark Crusade the Necron campaign narrator was a sentient Pariah, which had been thoroughly indoctrinated into the 'end all life' mindset. It was a near-unique occurence I believe, but the precedent is set- if you accept DoW as semi-canon, and bear in mind that the canonicity of all things varies from game to game and writer to writer (burn Ward).
If one of your players were to find- or create- such an entity as that Pariah, AND were renegade without being allied to Chaos- by which I mean never dedicating anything to a Dark God or performing rituals or being anything with a psy rating- I could see such a thing as a Necron minion.
The important thing to remember is that while Chaos is all-pervading among renegades, not all renegades are allied to Chaos. Look at Xanthite inquisitors (Eisenhorn especially) or more famous Night Lords such as Zho Sahaal and the Prophet. Also consider the example of the Alpha Legion at the time of the Heresy- they aligned with Horus out of loyalty to the Emperor's ideals (whether they have remained true to their original purpose is up to debate, and may vary from warband to warband).
It is also important to remember that being 'aligned' to one of the four Powers does not necessarily mean that you revere or pay homage to that power. It just means that you happen to live your life in accordance with that powers wishes, and so its essence fills you more readily- in the Soul Hunter sage there is a 'Khornate' Night Lord who shouts things like 'Blood and skulls,' but he never actually reveres Khorne- to him, Chaos is just another tool or weapon.
The point I'm driving at is that utilizing Necrons may be possible for a renegade, but it pretty much puts every Chaos-aligned faction diametrically opposed to you quite naturally. Which is not to say that you won't attract the interest of the Dark Mechanicus, radical Ordo Xenos inquisitors or the Eldar.
As a GM, I'd actually see Necron minions as a fantastic plot hook and way to screw with the players.