More uncertainty
> Could M2P2 still provide sufficient magnetic shielding?
Nobody knows for sure: if the plasma expansion takes place as modeled, it might; but controlling the plasma for any purposes at the scale one would need for either shielding or propulsion is a major challenge yet to be addressed. In other words: M2P2 is an emergent technology worth studying - for eg, it could be the simplest way of moving potential impactor objects out of Earthcrossing orbit; because the plasma could be made from in situ material quite easily - & would make missions like a Neptune/Uranus orbiter a lot easier; but not for spending huge amounts of pork as though it were a done deal.
Robert