Everyone is going to give you the standard "no" answer. Would I do it, probably not. Do I think the rest of the trailer could handle it, most likely. I've seen lots of homemade trailers and trailers made from mobile home frame/ axles that carry far more than I would put on them. The 3 biggest things are the tires, suspension, and brakes. The biggest problem with swapping them out is going to be the cost vs just selling what you have and getting what you need.
As far as an accident goes, I'm not sure why people keep talking about someone pulling out in front of you, first that's not your fault, secondly that's not going to put a lot of stress on the trailer's frame, the brakes yes, but those would be upgraded. Where you could run into trouble would be if going around a corner and the trailer frame fails causing your load to fall off and onto another vehicle.
As for weight the trailer will hold once you modify it the original tag is meaningless. You can reregister it as homemade where you can set the weight it's rated for. But, again, by the time you buy replacement axles (you'll find your wheel's bolt pattern is now wrong), tires/ wheels, and new springs I doubt you'll save any money.