True... I understand where you are coming at but the finals should be the most intense and have the hardest maps (if we assume maps scale in difficulty) with the two strongest competitors.
Thus, for example you have [30k vs 40k] and [90k vs 100k] on an insane song with the former able to keep combos on it whilst the latter barely surviving, the finals would be a harder map with the victor of the higher bracket barely passing and the victor of the lower bracket hardly hitting notes, in which the finals would be a 1 way stomp.
I feel that if the beatmaps get harder over the tournament (in which i believe they should), by the finals the map difficulty would be too high for equal competition.
As such I believe it should be better to have randomized brackets earlier and in easier songs (in which we lower ranked players play more in) there will be a greater chance for victory as compared to the finals where the difficulty is played more by the higher rank.
TLDR: It'll be easier for lower ranks to win in easier songs that they usually play than harder songs the higher ranks play in a scaling competition. Also, 2 high ranks playing round 1 is going to be 2 x SS, gonna be a spinfest... that wouldn't be fun