I assume it would be safe to delete the DLC in the /cookedpc directory that I do not want? I don't want any of the pre-order DLC except for the finishers DLC. Has anybody else deleted these with no problems?

Didn't do it, but yes, works just fine.
Just make sure you back the files up in case you want them any time in the future. :-)

Why wouldn't you want them? Just delete the items after you make the game and leave the files in there if you think they are an unfair advantage.

over powering? Not the kind of thing a low level character would have?

I don't blame you for not wanting them. It's your game experience, not anybody else's. But how about leaving them and and selling them for orens! :P

(I concede that taking them out entirely if you are not going to use them is much more an immersive move. Cheers!)