What does an anti-roll bar do if it doesn't reduce grip? The bar literally links one wheel to the other taking load off one wheel and adding it to it's partner.
It seems to me that getting a roll centre outboard and controlling it's position in bump, roll, droop and all the combinations of the above going through a corner would be much harder to achieve than to find space for an ARB. And can you do all that and keep a sensible camber curve for the tyre?
Keep it simple.