Actually the wider the tyre, the lower the load rating - the perpendicular forces acting on the sidewalls, from the tyre face in contact with the road, will be greater the wider the tyre. As a result the tyre design demands a much higher stiffness sidewall for wide tyres. Therfore, generally the crap ride from low profile tyres is from two-fold effects - less sidewall profile to absorb shock, and stiffer sidewalls themselves.
Secondly, the lower the profile, the lower the load rating due to the same reason as above - there is more force being exherted by the tyre trying to negate the perpendicular force drawing the sidewall toward the centre of the tyre, versus foce trying to hold the tyre (and car) up in an axial direction. You will find that there are only a few 265/35 (GTR) size tyres that will meet the Nissan placard load requirements - ask Jamezilla who was defected for insufficient load rating on his GTR.
Lastly, legally you can only increase rim width by one inch (in Vic anyway). That would mean that the approx max increase in tyre width you can legally go is ~40mm, eg. for a R32GTR with factory 8" wide rims, the tyre is 225/50/16, you can go to a 9" rim, say R34GTR rim in 18x9, which is generally recommended to have no wider a tyre than a 265/35/18 tyre.