I think the actual problem with your example is that the Mavericks and LGB's are both proxy weapons (or NonAIVehicles, whatever OFP calls them) and you can only have one type of those per aircraft.
And, no, resistance doesn't fix that, you can cheat however and include other weapons such as guns or rocket launchers (like the FFAR tubes), DKM's OV-10 Bronco does a good job of that.