How can they 'kickout' Portsmouth unless they are wound up. They would then have to give the winners of the Spurs Fulham tie a bye through to the final as they could not reinstate Birmingham who have legitimately lost on the field. The FA rules probably do not cover such a move as to allow Brum back in.
Didn't a team lose a couple of seasons ago and then got let back in?
My memory's sketchy on it but I'm sure there's a precedent for this.