Van Der Vaart would be a depth option. I see no issues with having him as a bench veteran with potential upside. He should be very inexpensive. He is 31, his contract is over in 6 months, and he is having an off year.
We clearly need depth in the CAM position, and if we can't add much quality during the window, Van Der Vaart should be very cheap. If he's more than a few million, or a simple loan its an easy pass, but if the price is low, its a move that has little downside.
No one is claiming that Van Der Vaart would come in and we'd run our offense through him.
That being said, if we could line up a move for a better option I'd be all for it. He's not my first choice, but as I said before, its very low risk if the price is what it should be. Ie: the price for an underperforming 31 year old with 6 months left on his contract on a team that could realistically get relegated.