Also keep in mind, that if the model deploying the portal dies, the portal doesn't GET deployed. So your reserves never come onto the table. You also may not deploy a portal from a RJB or skyboard. As far as deploying a portal on the last turn, that wouldn't work either. Your reserves don't start coming onto the table until the turn after the portal is deployed. You would have to deploy it on the turn BEFORE the last turn. This would give your opponent's troops ample opportunity to try and surround your portal, and if they do, your reserves also cannot come onto the table, as you have to follow the rules for not coming within an inch of an enemy model unless assaulting. To be honsest, I think this would be an expensive way to try to pull a fast one in the end, if you're trying to pull table quarters or something, and like you said, it would be a pretty boring game as well. (unless you think it's fun trying to keep your WWP deploying unit alive) Actually, I suppose if you just ran a normal list, and had a WWP on a haemy or something, and then dropped a portal at the end of the game on turn 5 to just bring out some bikes or something that might work for table quarters, but isn't really worth the points you're spending on it to make it possible, IMO.
That is all.
CrimsonShadow