Don't think a Discord would be very beneficial, honestly. Been in plenty that have them, but they just distract from posting usually. Only thing I find Discord helpful for is answering questions timely and having collaborative convos, but I think that's more up to people's discretion whether they want to talk on something like Discord privately or through the PM system here.

As for a starting scenario, I think testing out some Duel Runners while the rest of the gang is doing something else (splitting the open to have some sort of action) might be a good way to kick things off. It'll evenly divide the players if everyone who can Turbo duel takes the Duel Runners out and the rest are back at base, leaving 3 in each place right now. Only issue I see there is guiding some form of action or event at the base to make it similarly exciting or at least create conditions for a story to start there, which the introduction of a new member to the gang could do.