do not use citra for bittering - a complete waste (see below).
the closest thing to tradition you could do here is use the williamette @ 60 mins to achieve 20 IBU. witbier traditionally have neither flavor nor aroma additions.
personally, i would use the warrior for bittering (you won't need much, probably less than half an oz) and then use a little citra for flavoring and aroma: 0.2-0.25 at 10 mins and the same amount at 1 min/flamout.
agree about the floral mildness, disagree about not using warrior. it doesn't matter what you bitter with. the flavor and aroma will be boiled away after 60 mins, leaving behind only bitterness. hence my advice to not use the citra. that expensive hop should be save for flavor and aroma when it's unique characteristics can shine through.