Earlier quoted context omitted.
Surely the MID would need to be slowly phased out or just capped?
I would think so. Assuming it was politically feasible at all, it seems like it would need to be phased in. Or at least announced quite publicly that loans originated after a particular date could not have their interest deducted. It's not particularly fair to existing homeowners to eliminate the deduction after they've already purchased a house.
That would probably cause a crash in the housing market and leave many homeowners underwater on their mortgages. Phasing it out gradually seems like a better approach to me.