Some characters are pretty influenced by stage bans being present or not, especially mid tiers. Bo5’s also allow more time for adaptation, which is crucial in competitive melee.
Options could be between - “preference for Bo3”, “Preference for Bo5”, and “No Preference” to queue for both.
If players are willing to wait longer for Bo5 matches provided the queue time increases, that is their choice. If it bothers them that much, they can simply queue for both.

personally i think every set in ranked should be best of 5 but then if you are down 2 games, you are allowed to quit and a larger loss in elo