A strut brace would make very little difference to the handling on any of our cars, as the strut top isn't taking any side load like the earlier Nissans. We have upper wishbones taking the load, and our engine bays are braced/double walled.
The weak points are the main bolts under the chassis, where the large suspension bushes are located, like the main castor arm bush. These are flogging out badly after 10 years which shows the amount of load they deal with.