If I'm not mistaken, only Orly has sought to have a Judge "remove" Barry from office. Otherwise, it appears that the others have sought to have the courts make a Constitutional determination of weather or not Barry was/is eligible, and if not...find him ineligible. Actual removal would be by some other means as the Constitution only states how the removal of a POTUS is to be handled (not how to remove a usurper).
Unprecedented territory indeed.
But the plaintiff invoking the doctrine does not him or her self ask that the unconstitutional officer be removed. What the plaintiff asks is that the action by that officer which will affect him or her be declared as not lawful.
In the Hollister case the retroactity in question, as discussed by SCOTUS in the case cited by Hollister, the Ryder case, was whether Coastguardsman Ryder had raised the issue before the decision of the panel that affected him by a panel with an unconstitutional member. Thus SCOTUS explained that in order for government to function it was necessary that the party affected raise the issue before the decision in question was made because if every person, after had already been made, could challlenge the constitutional legitimacy of an officer involved in the decsion it would create chaos.
Teh question remains one of whether there is some reason that the doctrine as espoused would not apply to a de facto officer in the White House who is not de jure as oppposed to a lesser officer in that situation. Obviously, if Colonel HOllister succeeds, it will create a serious problem in that other members of the Reserves will wonder whether they should accept a call up order from the One. But Colonel Hollister has not asked for the removal of Soetoro a/k/a Obama only that if the defendant is found to be de facto and not then he must look for a legitimate call up order to Biden as the other interpleadler defendant.
If I was a lawyer, I would not push to have the courts remove him from office, I would have the courts open up the case for discovery to see whether he is eligible or not, and have Congress decided on what to do.....