I definitely agree this would be a nice feature. How often it would get used.. I am not so sure about, but it'd be great to have the option, with the correct skill-checks of course.
Also, since we are on the subject.. jumping off a roof with someone grappled. I would love this, also with the necessary skill-checks. Like a resist check and a shove check both before success.
Player A grapples Player B.
Player A shouts maniacally at Player B "We both die together, baka!"
Player A jumps off the s edge.
Player B is dragged along.
The possibilities.. mmmmm...