I don't think that you know how Usopp works- he's not the fighter so it is not expected from him to be strong in combat. True Hammer would be a good additional, great Usopp's hammer come back but Van Augur and Yasopp are not strong fighters but rather a support in the combat
![Kayneshrug :kayneshrug: :kayneshrug:](https://worstgen.alwaysdata.net/images/smilies/symbols/Kanyeshrug.png)
It would be just a support fight if you want them to fight