What I mean isn't just that Franky has things to do. I mean real development on Franky's passion for science and engineering, his nature as a cyborg, a real relationship with his idol. The problem is that due to everything else the arc has had to accommodate, there hasn't been any space or quiet moment to accommodate that.
That's why I believe all those things will take place after the arc, with Stella or one of the punks escaping on the Sunny to Elbaf.