IMO, the key issue (aside from RoF) is the insistence on going though Spa because the climbs in the area aren't hard enough. The best option (that I've come up with, at least) would be to head towards Malmedy climbing Côte du Pont like in 2017, then turning west into Stavelot to do Stockeu in full, 
north (harder) side of Wanne, then 
Hézalles, 
Brume, 
Chevron and 
Lorcé (minus the first kilometer) before Redoute, then Forges as the final climb at a little over 15k to go. Chevron would be at about 50k to go, Hézalles at less than 70k, Stockeu at about 80k. Wanne-north, Brume and Chevron are the only of these climbs that would be completely new to the race, afaik, as it draws on the early 90s routes.