I don't think it would be an issue at all. Why would it be? The average person, even the average mechwarrior, probably knows next to nothing about the Gladiator. I don't think there would be any kind of controvery that a primitive battlemech from 500 years ago wasn't very effective. I doubt the Combine would take any sort of official position on the mech at all. If anything, you'd have stories about "brave Combine soldiers, fighting in inferior, hastily-designed machines, defeated their enemies blah blah blah."
I can't imagine people today caring at all if you described the muskets that were used in the American Revolutionary War as "inferior to their British equivalents" or something like that. Sure the Combine is pretty uptight, but I just can't see it being something anyone cares about.