As long as the bias can be played with, theres no problem in terms of how the system will operate, its just that you are fitting something for nothing. It is extra unsprung weight but the ratio of sprung to unsprung weight will barely change so it shouldnt have any noticable effect on the handling. Im presuming this wouldnt affect the operation of the ABS system?
I find it funny that the supposedly knowledgable chap who is looking to do this finds the rear of his car quite skittish and yet thinks more braking power is needed at that end?

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