The. Cook's Illustrated that came today had
an interesting article about 1.5" or thicker
steak where you roast the steak in the oven
at 275F until the internal temp. is 90F and then
brown it on top of the stove. Look at:
http://cooksillustrated.com/byissue.asp#topOfPage
Why not try smoking the steak in your WSM or
equivalent to 90F, and then searing it on a very hot
grill?
I like to grill 2.5" thick sirloin[chateaubriand in Cal.] from the
butt end of the sirloin. This would be perfect
for that. It would give you a nice smokey flavor usually
lacking from grilled steak, and it would give you "char-rare",
as the above link shows.

Kent