With travel trailers, I think the tow vehicle requirements are more about the payload capacity rather than the tow capacity....especially with a 1/2 ton. 3/4 tons also have to be very careful especially when towing a pin heavy 5th wheel.
To answer your question, yes... you could increase the tow capacity by replacing the entire rear suspension (including the 3rd member and brakes) with a unit that does have the capacity. You'd probably have to do the front suspension also.
Might as well trade in the current truck for a more HD unit and not have to go to all the trouble...probably cheaper too.
Ron