It would be a nice addition, and probably not that hard to implement.
Add connect four?
I would argue that effort should be spent on Gomoku and Renju first. They're similar n-in-row family games. Maybe I'm wrong and connect four is more popular but idk.
It's a very good idea
I think connect 4 is more popular than Renju or Gomoku.
I used to play it on LUDOTEKA, and it was very easy to find opponents.