This is just an imaginary case. Like i mentioned last time; Redsquare's main vocalist Lina is a great singer and native English speaker. Or Secret Number's main vocalist Denise is an even better singer and native English speaker. imagine either of them as itzy member instead of Ryujin. Lia will not get that much flake for her dancing with another average dancer member and itzy will still have 3 out of 5 strong dancers. itzy can promote to the West better with two English speakers. Lia has learned English from international school; she hasn't lived outside of korea. With another good main vocalist; it will give them musically more variety too. Like Denise can sing variety of songs and with her; the group would be less rap based and more vocal based.
From what i've seen; itzy members have individual images but Ryujin's seemed to be about her being a leader. Lia is elegant and well spoken; Yeji has fierce looks and athletic style; Chaeryeong has very feminine personality and style; and Yuna has bubbly and charming personality which means she can do well in Western interviews like Jhope and Jimin even if she can't speak English well.
itzy has strong performers like bts; but bts has strong rappers and 4 vocalists compared to itzy. Just from perspective of doing well in the US.
Lina:
Denise: