This shouldnt be a problem if you use non ABS brake lines and compensators. The bias can be adjusted with the angle the compensators are set at. Much better than trying to bodge the ABS setup to work right with or without rear disks and uprated brakes etc.

Gus what tyre size are you running with 17in wheels and height etc. I would say that running a size down at 16in would make a big of difference to overall handling per lap time. The rack brackets will effect bump steer if on road but on track its more to do with keeping the arms at a straight angle to the hubs. Will give a better steering angle on hard corners too if you have the correct stiffness on the front.