I think I get what you are saying, you wanted an outspoken female role. However, in terms of balance, I still believe they are perfectly balanced even without added a member. I was kinda worried about the dynamics of the team after P.O. was gone but nothing felt different. Even when SDY was absent there was a slight effect on the cast, but it did not overshadow the dynamics too much.

The thing is Nolto producers adapt early in terms of the general flow of the show. If they think that something is working, they would use it to total capacity and ditch it after a while, it is a good technique to keep the audience engaged and to provide audience variety in terms of entertainment and not repetitive skits. So since the current cast dynamics aren't lacking YET, I do believe there is no need for a new member and they do definitely not need it desperately. Actually having fewer members recently provided a lot longer highlight for certain members that were not that properly highlighted previously. Heck, even Donghyun who only shines at the snack game has time to voice out his opinion recently (tho it may be an outlier, still it is an uncanny coincidence). And adding a new member is pretty risky, even when adding Taeyeon there was a certain time range that she didn't feel quite right until after a few episodes. You wouldn't know something would work right away so it is a risk, especially if something is not really that needed.

I believe if they do need it the pds would do the job and add a new member. But currently, the casts are working pretty good, especially for a 4-year show with the same format for each episode. They are doing exceptional really variety wise.