Donna the little mellers isn't even there yet and you are already designing a home, way to go girl!!
Just a couple of ideas, get one large branch for the 'anchor' piece. If you can get one nearly as long as your free range area with several branches coming out of it. Anchor this to the ceiling really well and sort of build out from it. That is part of what I once planned to do

before I gave up the idea of a mellers. We took a about an 8 ft branch, cut off all limbs going toward the ground, used the ones going up. Worked some large bio vine, lots of different sizes of branches a couple of old tie downs (mesh, nylon ?? not sure what they are made of) bought for the back of hubby's pick up, lots of fishing line wrapping the joints reforced with hot glue, and attached several places to the wall.
Mine you after building this I never used it (hubby not happy he had it build it 'for nothin') because i decided on using the space for quads & jacksons.