A lot of our couples lately have had uneven wedding parties!! I definitely don't think it's weird. As essandpea said, you have to pick and choose what traditions are right for you and your fianc©, these day's it's definitely not necessary to follow the rules.
Have 2 girls per guy (what guy doesn't like that if you're going to have them announced into the reception or walk down the aisle for the ceremony (or maybe consider having the guys up at the front for the beginning of the ceremony and just the girls walk down the aisle).
Also, from a photographic stand point having an uneven bridal party is fun and forces the photographer to get creative and mix it up when it comes time for the wedding party pictures!