Hmmm lets try and answer them one at a time

When i said "
you can counteract it with stiffer springs but the ride quality suffers as a result." what i meant was.... Removing the anti roll bar obviously induced more roll in the car and the theory is that what it is solving is the inside wheel lift under hard cornering. If the front wheels are no longer connected then as the outside wheel dips in to the body under cornering then the inside wheel will not want to follow suit because it is not being pulled up by the ARB. However by removing the ARB to solve this you are allowing a much more severe amount of weight transfer towards the outside of the car during cornering, so this is taking weight off the inside wheel and reducing grip anyway.
Now if you do remove the ARB you will need to stiffen the springs up to counteract this body roll. So on a car as heavy as the 405 removing the ARB, which is fairly thick, will need something in the region of 400-500 pound springs and some stiff dampers to control them, to get it somewhere back to where it was in terms of body roll, which is obviously going to affect the ride quality on the road quite badly, not to mention the wet handling.
And lets not forget that the arb only works when cornering so you effectivly have a 2 springs working all the time and one spring that only works when it's needed instead of 2 springs trying to do 3 springs job and working all the time.
As for the 205's i presonally like it hard at the front and just slightly softer at the back. It's all down to presonal preferance.
Hope this all helps.