Well it really depends where you want the "center" of the track to be in terms of freestyle.
if you want it to be the center, then the track would have to encorage coming back to the middle of the track and using the racing pyramids and catch ramps to fly off to another part of the track without loosing speed. as well as putting obsticles and berms in the outer fields that lead into other obsticles or berms that could in theory all bring you back to the middle again to have another go around, like a mobious strip of freestyle obsticles.
if i were to suggest anything right now, it'd to put a few dual sided triangularly shaped ramps in the crux between the launch pyramids and the catch ramps next to them, so you could fly across the gap in the middle to the far catch ramp or fly over the closest pyramid and bank off to another part of the field, or just throw you into the big pit in the middle to hit something from the backside to get out again.
mabye a few busses in the outfeild dirt patch between the turns with a ramp on each one (symetrically) pointing towards the conglomorate in the middle, again, forcing you nearer.
other then that i can't conjure much else. sorry