No, I think that might be the loophole. If you make a deal with Boston you can bypass the waiver wire. But it is admittedly not clear. It would be a good reason for Boston to do it though, because if the Phillies remove him from the roster or trade him he will almost certainly never rejoin the Red Sox (since like you say a bad team will carry him into next May no problem) so why not get something for him?
Rule 5 Draft picks... must be placed on outright waivers in order to be removed from the 26-man roster in the subsequent season. Should the player clear waivers, he must be offered back to his previous team for $50,000 and can be outrighted to the Minors only if his original club does not wish to reacquire him.
Clubs may trade a player selected in the Rule 5 Draft, but the same restrictions apply to the player's new organization. However, a club may also work out a trade with the Rule 5 pick's original club to acquire his full rights, thereby allowing him to be optioned to the Minors under traditional circumstances.
