The point I was making, since this was when the FWL was breaking up and interstellar communication is spotty . . . how would they know what a Marik prototype would look like? Its not like they would have had moles inside Irian . . . Ronin on Wallis might have, but even that is doubtful. Ronin rushed the Patriot into design at Regulus behest as the League started to break up, dusting off a design in the works or one that the LCCC had declined to buy in the Pikeman (does make me wonder what it might have looked like). So for '67-'71 it would not have been a stretch for Irian, one of the biggest and most powerful producers in the League, to dust off a design that was never produced that Regulus would never have known about.
Point is moot though . . if you do not think they could have done it, then if this ever gets played out on your table- by all means, no Celestials. But IMO its a possibility they could have been there in the vanguard as a combat test where Blakists could have controlled the zone, and then pursuit and the total destruction of the survivors could have been done by more normal Marik affiliated equipment.