In your design, how do you connect to the TTC / Magic Kingdom? Do all trains fork onto the parallel tracks to TTC at the point near World Drive and Epcot Center Drive? I think it will be quite a long ride for some connections, like Epcot to Magic Kingdom. Either one way or the other, you'd have to travel almost all the way around the loop. Or between Animal Kingdom and Epcot in one direction or the other, you'd have to up the TTC spur and back.
Now if your new loop were parallel bidirectional tracks all the way then it could work. Where the track exits the Epcot station, connect it to the right (east) side of the current parallel track. The left side gets extended in an outer loop around Future World, then continues around your loop to HS, AK, any other stops, and then back up the west side of World Drive to the TTC. Build a parallel track along the same route in the reverse direction until it connects back to the original Epcot track (the inner Epcot loop) at the entrance to Epcot.