As for cars intentionally designed to be inherently [under|over]steery, I think it's reasonable to assume that Ross Brawn's car design philosophy (as in his days with Rory Byrne at Ferrari) is to make it as neutral as possible and responsive to a wide spectrum of setup changes required by opposing driver styles. It's unfortunate how slight miscalculations (or misjudgments) in a couple of variables have given the W01 an inherent behavior that does not respond too well to Schumacher's (and Shovlin's) attempts to set it up for his on-the-edge driving style.
I certainly hope the Barca B-spec will allow Michael to regain his confidence in the car to attack with full commitment. Ability-wise, I'd like to believe that Michael's still got a dormant 8/10ths or more from his glory years waiting to be unlocked, so long as the car setup and confidence issues are thoroughly sorted out. But the longer this takes to happen, the greater his frustrations and self-doubts will become.