Depending on the looks, and the amount of 'rot' I'd say that once you are this far, you might as well keep it, mainly as then you will not lose too much of your time and money. But like you said, pictures speak louder than words.
Having a vehicle ready to drive around in, means you can take your time finding a nice 200Tdi engine and pop that one in. It will boost your vehicle's value by the same amount as you would have paid for the much more loved 200Tdi...