IIRC, in the pnp, having a xeno, especially a troublesome one like an Ork, nevermind a DEldar, is a literal drain on your resources, as it takes a penalty on your morale stat of your ship, 1 point of your total crew members (because the Deldar had to torture people to live), and so on. Sadly, the numbers were too small to be anything more than a nuisance... Although the rules pretty much told you that having a DEldar is inviting him to backstab you sooner than later. Or stumble upon a particularly close-minded Inquisitor.
I dunno if this game will make it a problem for you to have a DEldar.