I think this is a necessary area for all modern Wing Chun guys to learn. Especially since grappling and MMA is so common now. My background taught us not to go to the ground for multiple reasons. Do I like to grapple? Man, it's a blast, it's just not WC. From the ground, you can't fight 2 or more people, it's not consistent with using less to do more, etc. All this said, I try to work WC against takedowns on a regular basis. In fact, I now teach a proper fighting stance by trying to grab the students torso (grappler takedown to the waist) while they keep their hands in place. From there, after they learn some basics, I not only teach them to use basics against punching, but against kicks, as well as the grappling takedown. I think it is unrealistic to only train against punches around the four corners area. Much better, in my opinion, to teach someone early how to counter a wide variety of moves, i.e. boxing, kickboxing, grappling, etc.
Another one of my opinions is that a great deal of "WC versus" moves are unrealistic. Only teaching someone to tan da against a jab is going to get them beat up. The same applies when using WC against a grappler. Each engagement is different, I think it is just the most important that you work against a realistic attack. Sure, start with the slow, stiff zombie punch to let them learn the move, but definitely pick up the heat to force the hands to be correct under pressure. Teaching someone to immediately close distance and engage centerline without telegraph is a much better concept to teach first, and have tan da as one of many tools to use. What I see a lot of guys do is teach moves instead of concepts. I think it's much wiser to teach them basics, and then just come after them, including the grappling takedown, and allow them to use what works for them. People are usually afraid that their instructor is going to get mad if they don't do sissy hits, so I just keep telling them to hit harder and engage more until they are neutralizing my attack.
I do, however, think that even if you're taken to the ground, there is still plenty you can do. If someone has me in the mount, first thing I am going for is the groin, and when they guard that, they're going to get multiple bil tzes and sats to the throat. The guard, for me, is just bringing their centerline real close so I can pound on it. Still don't understand why this concept is not brought up more. I guess cause so many think that MMA is the only real fighting realm now. The reason we don't see strikes to the groin and throat while the attacker is in the mount is because it's illegal in MMA. Why? Because you can really hurt someone; and that's why I would do it. But WC is not a tournament sport, it's me stopping someone who is in the wrong, i.e. home invader at night, rapist, etc.
Going to post some videos soon to explain concepts.