I teach WC as an attachment art. Meaning we need to be in bridge contact for WC tools to be used. Until than it will resemble MMA. I use slight pock sau's to keep the Jab, Cross out and cover like a boxer for the hooks and high kicks. Only when I bridge and make contact and attach to the opponent does WC come in. You need to stay alive on the outside until you can bridge. Through sparring you will find that attempting to stop hooks with Tan Da or Woo Da or what ever is a guessing game that I don't play. I cover and sometimes use the cover as an elbow attack.
Even beginners should spar. What WC techniques we trained at the beginning of class will be the focus in sparring at the end of class.
I train BJJ and we do it the same way. No need to re-invent the wheel, go with what works to build competent fighters.
Once contact is made, wing chun 'tools' still should be visable, right?
I don't think anyone will disagree with you that people should spar, but the BIG question is, what constitutes as sparring. Quite a few people see sparring as the western boxing type of exchange, and some even veiw sparring as fighting (I kid you not, this is the honest truth)