It can work, the roots will provide the low-RPM boost
but them later, the ATI (let's say) will feed pre-pressurized
air to the roots, allowing more capability for the roots.
But actually, a properly sized ATI or a roots is plenty
on any V6, a big autorotor will do as much as what you ask.
The P1SC (ATI) is big enough to make low-end boost
on even a 5.0 if properly pullied. I've seen it. Proper sizing
is much better than trick setups like this guy wants. You do
not have the knowledge to make it work, or you would not ask
these Q's so it is best to tell the customer that or risk being
sued and if it does not work for him (and I doubt it will) you
would lose out too, and end up losing $$$ very likely, or making
an enemy or getting sued. Or all 3