I don't foresee any easy way to truly seed 8 players out of 16 berths spread across 5 leagues, most of whom have no matches against anyone outside their league. If there were 4 leagues, you could just seed the #1 and #2 players from each one, and go from there, but with 5, it would be very difficult. There would inevitably be some unfair losses and ADs complaining that their player was screwed.
Besides, they have been doing a full double elimination in 3A and 4A for the last (at least) 6 years. I really don't see why they would try something completely different? But really, it is the (No Booing!)WIAA, so who knows.