I just took a look at Wookieepedia, and I think that most of the notable practitioners held thier lightsabers in the standard way, and some of them used double sabers:
I think that the main thing about Shien is that it isn't a purely defensive style: after a defensive parry, there is an aggressive counterstrike; likewise, blaster bolts get deflected back at attackers, rather than at innanimate objects. The hand grip position being reversed can be used, but isn't the primary use of the form.
Aside from that, while it would be possible to make some hilts with reversed grips, I don't think that the animations sync up as well, and therefore wouldn't be worth the effort. You'd have to use two sabers, because holding a sinigle blade upside down with two hands looks funny