I guess the obvious solution is you have to make it practically impossible to miss, and obvious to all, that they are still fitted. Does this mean extra, extra long tails? Tying them back to the nose gear pin so they have to come off/out as a set? Tying them back to the towbar? Something like that? Unfortunately this probably means that the covers in use are airport specific, as the aircraft carried ones would not usually need the extra fittings (if any). During pushback/engine start when the pilot is talking to the guy on the headset, surely it would not be too hard for a challenge and response to be implemented somewhere in that exchange.