There are 1,000's of us running 33x12.5's on 7" rims...and no one has had a problem yet.
I ran jeeps like that, and now X's run like that...its fine.
For street performance, generally, you want the rim width to equal the tread width (The sidewall and tread width are not the same thing...sidewall widths are wider)...as it makes a nice flat foot print with less tire roll.
For offroad, some sidewall flex is desireable, as it helps the tire wrap around rocks, get grip, etc.
As a compromise, a 7" rim is good to go...and has been a reliable solution. An 8" rim also works fine.
The BS issues are your bogey though...the less BS, the more the tire sticks out, and the more it will hit as you turn the wheel, as the tires are swinging through a wider arc.
Because BS is a hub face to inner lip measurement...changing rim width won't hurt the clearance if the BS is the same.
_________________________
- TJ
2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....
Friends don't let friends drive stock.
http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif