Some have done it, no worries or problems. I agree that a 7000 lb load rating is very marginal for a fully loaded Elite II when you take it off smooth roads. The bigger coupler will fit, just drill a new set of bolt holes in the right place, that is the tricky part. If you use an Andersen hitch, replacing the ball assembly is more costly than a $15 Walmart deadweight ball.
The tongue will sit a little higher, not a big deal....
The trailers should come this way from the factory. But I think they want as much commonality as possible, which explains the weird six bolt wheels on 3500 pound axles, to match the wheel pattern on the Elite with its single heavier axle. It is good for the factory guys, but not for an owner who wants disc brakes and must swap axles or buy a new set of five bolt wheels....! Grrrr.
I may upsize, but I may go to an offroad coupler and lose the ball entirely.
Go for it. Take pictures.
John Davies
Spokane WA