1) I think it's going to happen, and offsite folks are legitimate,as are people without MB's like myself.....
2) Disney bus transport has always been a part of being at Disney, so I don't think there's a valid way to check onsite visitors at buses,etc.
3) But that's different than parking- a simple timed ticket with a time stamp on it should suffice,as most parking garages use that. I think this will cut down on people visiting a resort just to eat though which will hurt revenue,I assume that's a big source of income for Disney... I wouldn't pay 40 bucks pp to eat at Chef Mickeys and then pay for parking also.....
4) And I personaly prefer parking to be a separate cost vs. 'incorporated' into the hotel cost...so those who don't have a car aren't paying for that.