I think I understand what the OP wants. He wants to move the tongue jack to the aluminum I beam frame so he can put a smaller winch tower more rearward under the bow. This will leave room on the tongue to put a folding tongue assembly on the trailer.
I wouldn't put the tongue jack on the aluminum I beam frame without beefing up the place where you are going to attach it. I am no aluminum trailer expert but I wouldn't put that load on the edge of an aluminum flange. There are several ways you could do it. I would put a couple of aluminum plates, one top and one bottom (1/4" x approx. 6" x whatever the width of the trailer frame is where the attachment point is, may work) . These plates would go from one side of the trailer frame to the other, where the tongue jack is going to be installed. Obviously the ends of these plates would have to be angled to match the shape of the trailer frame. I would then weld a steel strip on the steel jack mount to attach to these plates, right through the I beam flange, top and bottom. This will spread the load across the entire frame instead of on the flange edge of one side.
There are others ways to accomplish this such as boxing the section of frame where the mount would go. I'm just trying to accomplish the reinforcement without have to weld to the aluminum trailer frame.
Also, I always mount my tongue jacks on the port side of the trailer. This is so one person, the driver, can jack up the trailer without changing sides.
I put my spare tire mounts on the starboard side of the trailer so you don't have to remove the spare tire on the traffic side of the trailer.